diff --git a/system/Database/BaseBuilder.php b/system/Database/BaseBuilder.php
index 2384ac515d8d..d62bca882fd6 100644
--- a/system/Database/BaseBuilder.php
+++ b/system/Database/BaseBuilder.php
@@ -1251,7 +1251,7 @@ public function orderBy(string $orderBy, string $direction = '', bool $escape =
 
 		if ($escape === false)
 		{
-			$qb_orderby[] = [
+			$qb_orderBy[] = [
 				'field'     => $orderBy,
 				'direction' => $direction,
 				'escape'    => false,
@@ -1259,10 +1259,10 @@ public function orderBy(string $orderBy, string $direction = '', bool $escape =
 		}
 		else
 		{
-			$qb_orderby = [];
+			$qb_orderBy = [];
 			foreach (explode(',', $orderBy) as $field)
 			{
-				$qb_orderby[] = ($direction === '' && preg_match('/\s+(ASC|DESC)$/i', rtrim($field), $match, PREG_OFFSET_CAPTURE))
+				$qb_orderBy[] = ($direction === '' && preg_match('/\s+(ASC|DESC)$/i', rtrim($field), $match, PREG_OFFSET_CAPTURE))
 					?
 					[
 						'field'     => ltrim(substr($field, 0, $match[0][1])),
@@ -1278,7 +1278,7 @@ public function orderBy(string $orderBy, string $direction = '', bool $escape =
 			}
 		}
 
-		$this->QBOrderBy = array_merge($this->QBOrderBy, $qb_orderby);
+		$this->QBOrderBy = array_merge($this->QBOrderBy, $qb_orderBy);
 
 		return $this;
 	}
diff --git a/system/Database/BaseConnection.php b/system/Database/BaseConnection.php
index 7e163304a252..c278568f1e33 100644
--- a/system/Database/BaseConnection.php
+++ b/system/Database/BaseConnection.php
@@ -422,12 +422,14 @@ public function initialize()
 	 * @param  boolean $persistent
 	 * @return mixed
 	 */
-	abstract public function connect($persistent = false);
+	abstract public function connect(bool $persistent = false);
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Close the database connection.
+	 *
+	 * @return void
 	 */
 	public function close()
 	{
@@ -526,9 +528,9 @@ public function getError()
 	/**
 	 * The name of the platform in use (MySQLi, mssql, etc)
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getPlatform()
+	public function getPlatform(): string
 	{
 		return $this->DBDriver;
 	}
@@ -538,9 +540,9 @@ public function getPlatform()
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	abstract public function getVersion();
+	abstract public function getVersion(): string;
 
 	//--------------------------------------------------------------------
 
@@ -586,7 +588,7 @@ public function addTableAlias(string $table)
 	 *
 	 * @return mixed
 	 */
-	abstract protected function execute($sql);
+	abstract protected function execute(string $sql);
 
 	//--------------------------------------------------------------------
 
@@ -599,13 +601,13 @@ abstract protected function execute($sql);
 	 * queries if needed.
 	 *
 	 * @param string  $sql
-	 * @param array   ...$binds
+	 * @param mixed   ...$binds
 	 * @param boolean $setEscapeFlags
 	 * @param string  $queryClass
 	 *
 	 * @return BaseResult|Query|false
 	 */
-	public function query(string $sql, $binds = null, bool $setEscapeFlags = true, $queryClass = 'CodeIgniter\\Database\\Query')
+	public function query(string $sql, $binds = null, bool $setEscapeFlags = true, string $queryClass = 'CodeIgniter\\Database\\Query')
 	{
 		if (empty($this->connID))
 		{
@@ -713,6 +715,8 @@ public function simpleQuery(string $sql)
 	 * Disable Transactions
 	 *
 	 * This permits transactions to be disabled at run-time.
+	 *
+	 * @return void
 	 */
 	public function transOff()
 	{
@@ -750,7 +754,7 @@ public function transStrict(bool $mode = true)
 	 * @param  boolean $test_mode = FALSE
 	 * @return boolean
 	 */
-	public function transStart($test_mode = false)
+	public function transStart(bool $test_mode = false): bool
 	{
 		if (! $this->transEnabled)
 		{
@@ -767,7 +771,7 @@ public function transStart($test_mode = false)
 	 *
 	 * @return boolean
 	 */
-	public function transComplete()
+	public function transComplete(): bool
 	{
 		if (! $this->transEnabled)
 		{
@@ -924,7 +928,7 @@ abstract protected function _transRollback(): bool;
 	/**
 	 * Returns an instance of the query builder for this connection.
 	 *
-	 * @param string $tableName
+	 * @param string|array $tableName
 	 *
 	 * @return BaseBuilder
 	 * @throws DatabaseException
@@ -1008,7 +1012,7 @@ public function getLastQuery()
 	 *
 	 * @return string
 	 */
-	public function showLastQuery()
+	public function showLastQuery(): string
 	{
 		return (string) $this->lastQuery;
 	}
@@ -1023,7 +1027,7 @@ public function showLastQuery()
 	 *
 	 * @return float
 	 */
-	public function getConnectStart()
+	public function getConnectStart(): float
 	{
 		return $this->connectTime;
 	}
@@ -1038,9 +1042,9 @@ public function getConnectStart()
 	 *
 	 * @param integer $decimals
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getConnectDuration($decimals = 6)
+	public function getConnectDuration(int $decimals = 6): string
 	{
 		return number_format($this->connectDuration, $decimals);
 	}
@@ -1067,14 +1071,14 @@ public function getConnectDuration($decimals = 6)
 	 * insert the table prefix (if it exists) in the proper position, and escape only
 	 * the correct identifiers.
 	 *
-	 * @param string|array
-	 * @param boolean
-	 * @param mixed
-	 * @param boolean
+	 * @param string|array  $item
+	 * @param boolean       $prefixSingle
+	 * @param boolean       $protectIdentifiers
+	 * @param boolean       $fieldExists
 	 *
 	 * @return string|array
 	 */
-	public function protectIdentifiers($item, $prefixSingle = false, $protectIdentifiers = null, $fieldExists = true)
+	public function protectIdentifiers($item, bool $prefixSingle = false, bool $protectIdentifiers = null, bool $fieldExists = true)
 	{
 		if (! is_bool($protectIdentifiers))
 		{
@@ -1313,7 +1317,7 @@ public function escapeIdentifiers($item)
 	 * @return string
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function prefixTable($table = '')
+	public function prefixTable(string $table = ''): string
 	{
 		if ($table === '')
 		{
@@ -1334,7 +1338,7 @@ public function prefixTable($table = '')
 	 *
 	 * @return string
 	 */
-	public function setPrefix($prefix = '')
+	public function setPrefix(string $prefix = ''): string
 	{
 		return $this->DBPrefix = $prefix;
 	}
@@ -1356,7 +1360,7 @@ abstract public function affectedRows(): int;
 	 * Escapes data based on type.
 	 * Sets boolean and null types
 	 *
-	 * @param $str
+	 * @param mixed $str
 	 *
 	 * @return mixed
 	 */
@@ -1395,9 +1399,9 @@ public function escape($str)
 	 *
 	 * @param  string|string[] $str  Input string
 	 * @param  boolean         $like Whether or not the string will be used in a LIKE condition
-	 * @return string
+	 * @return string|string[]
 	 */
-	public function escapeString($str, $like = false)
+	public function escapeString($str, bool $like = false)
 	{
 		if (is_array($str))
 		{
@@ -1473,7 +1477,7 @@ protected function _escapeString(string $str): string
 	 * @return boolean
 	 * @throws DatabaseException
 	 */
-	public function callFunction(string $functionName, ...$params)
+	public function callFunction(string $functionName, ...$params): bool
 	{
 		$driver = ($this->DBDriver === 'postgre' ? 'pg' : strtolower($this->DBDriver)) . '_';
 
@@ -1507,7 +1511,7 @@ public function callFunction(string $functionName, ...$params)
 	 * @return boolean|array
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function listTables($constrain_by_prefix = false)
+	public function listTables(bool $constrain_by_prefix = false)
 	{
 		// Is there a cached result?
 		if (isset($this->dataCache['table_names']) && $this->dataCache['table_names'])
@@ -1566,7 +1570,7 @@ public function listTables($constrain_by_prefix = false)
 	 * @param  string $table_name
 	 * @return boolean
 	 */
-	public function tableExists($table_name)
+	public function tableExists(string $table_name): bool
 	{
 		return in_array($this->protectIdentifiers($table_name, true, false, false), $this->listTables());
 	}
@@ -1581,7 +1585,7 @@ public function tableExists($table_name)
 	 * @return array|false
 	 * @throws DatabaseException
 	 */
-	public function getFieldNames($table)
+	public function getFieldNames(string $table)
 	{
 		// Is there a cached result?
 		if (isset($this->dataCache['field_names'][$table]))
@@ -1637,11 +1641,11 @@ public function getFieldNames($table)
 	/**
 	 * Determine if a particular field exists
 	 *
-	 * @param  string
-	 * @param  string
+	 * @param  string   $fieldName
+	 * @param  string   $tableName
 	 * @return boolean
 	 */
-	public function fieldExists($fieldName, $tableName)
+	public function fieldExists(string $fieldName, string $tableName): bool
 	{
 		return in_array($fieldName, $this->getFieldNames($tableName));
 	}
@@ -1735,7 +1739,7 @@ public function resetDataCache()
 	 *
 	 * @return array
 	 */
-	abstract public function error();
+	abstract public function error(): array;
 
 	//--------------------------------------------------------------------
 
@@ -1744,7 +1748,7 @@ abstract public function error();
 	 *
 	 * @return integer
 	 */
-	abstract public function insertID();
+	abstract public function insertID(): int;
 
 	//--------------------------------------------------------------------
 
@@ -1755,7 +1759,7 @@ abstract public function insertID();
 	 *
 	 * @return string
 	 */
-	abstract protected function _listTables($constrainByPrefix = false): string;
+	abstract protected function _listTables(bool $constrainByPrefix = false): string;
 
 	//--------------------------------------------------------------------
 
@@ -1803,12 +1807,19 @@ abstract protected function _foreignKeyData(string $table): array;
 
 	//--------------------------------------------------------------------
 
-	public function __get($key)
+	/**
+	 * @param string $key
+	 *
+	 * @return mixed
+	 */
+	public function __get(string $key)
 	{
 		if (property_exists($this, $key))
 		{
 			return $this->$key;
 		}
+
+		return null;
 	}
 
 	//--------------------------------------------------------------------
diff --git a/system/Database/BasePreparedQuery.php b/system/Database/BasePreparedQuery.php
index 887f906e5b46..a4287c2d25b9 100644
--- a/system/Database/BasePreparedQuery.php
+++ b/system/Database/BasePreparedQuery.php
@@ -37,6 +37,7 @@
 
 namespace CodeIgniter\Database;
 
+use CodeIgniter\Database\MySQLi\Connection;
 use CodeIgniter\Events\Events;
 
 /**
@@ -85,7 +86,7 @@ abstract class BasePreparedQuery implements PreparedQueryInterface
 
 	public function __construct(ConnectionInterface $db)
 	{
-		$this->db = & $db;
+		$this->db = &$db;
 	}
 
 	//--------------------------------------------------------------------
@@ -103,7 +104,7 @@ public function __construct(ConnectionInterface $db)
 	 *
 	 * @return mixed
 	 */
-	public function prepare(string $sql, array $options = [], $queryClass = 'CodeIgniter\\Database\\Query')
+	public function prepare(string $sql, array $options = [], string $queryClass = 'CodeIgniter\\Database\\Query')
 	{
 		// We only supports positional placeholders (?)
 		// in order to work with the execute method below, so we
@@ -180,9 +181,9 @@ public function execute(...$data)
 	 *
 	 * @param array $data
 	 *
-	 * @return ResultInterface
+	 * @return boolean
 	 */
-	abstract public function _execute($data);
+	abstract public function _execute(array $data): bool;
 
 	//--------------------------------------------------------------------
 
@@ -196,7 +197,9 @@ abstract public function _getResult();
 	//--------------------------------------------------------------------
 
 	/**
-	 * Explicity closes the statement.
+	 * Explicitly closes the statement.
+	 *
+	 * @return null|void
 	 */
 	public function close()
 	{
@@ -232,7 +235,7 @@ public function getQueryString(): string
 	 *
 	 * @return boolean
 	 */
-	public function hasError()
+	public function hasError(): bool
 	{
 		return ! empty($this->errorString);
 	}
diff --git a/system/Database/BaseResult.php b/system/Database/BaseResult.php
index ca7f11bb788f..5b2267d14b05 100644
--- a/system/Database/BaseResult.php
+++ b/system/Database/BaseResult.php
@@ -123,9 +123,9 @@ public function __construct(&$connID, &$resultID)
 	 *
 	 * @param string $type The row type. Either 'array', 'object', or a class name to use
 	 *
-	 * @return mixed
+	 * @return array
 	 */
-	public function getResult($type = 'object'): array
+	public function getResult(string $type = 'object'): array
 	{
 		if ($type === 'array')
 		{
@@ -291,12 +291,12 @@ public function getResultObject(): array
 	 *
 	 * If row doesn't exist, returns null.
 	 *
-	 * @param integer $n    The index of the results to return
+	 * @param mixed   $n    The index of the results to return
 	 * @param string  $type The type of result object. 'array', 'object' or class name.
 	 *
 	 * @return mixed
 	 */
-	public function getRow($n = 0, $type = 'object')
+	public function getRow($n = 0, string $type = 'object')
 	{
 		if (! is_numeric($n))
 		{
@@ -336,7 +336,7 @@ public function getRow($n = 0, $type = 'object')
 	 *
 	 * @return mixed
 	 */
-	public function getCustomRowObject($n, string $className)
+	public function getCustomRowObject(int $n, string $className)
 	{
 		isset($this->customResultObject[$className]) || $this->getCustomResultObject($className);
 
@@ -364,7 +364,7 @@ public function getCustomRowObject($n, string $className)
 	 *
 	 * @return mixed
 	 */
-	public function getRowArray($n = 0)
+	public function getRowArray(int $n = 0)
 	{
 		$result = $this->getResultArray();
 		if (empty($result))
@@ -391,7 +391,7 @@ public function getRowArray($n = 0)
 	 *
 	 * @return mixed
 	 */
-	public function getRowObject($n = 0)
+	public function getRowObject(int $n = 0)
 	{
 		$result = $this->getResultObject();
 		if (empty($result))
@@ -412,8 +412,8 @@ public function getRowObject($n = 0)
 	/**
 	 * Assigns an item into a particular column slot.
 	 *
-	 * @param $key
-	 * @param null $value
+	 * @param mixed $key
+	 * @param mixed $value
 	 *
 	 * @return mixed
 	 */
@@ -450,7 +450,7 @@ public function setRow($key, $value = null)
 	 *
 	 * @return mixed
 	 */
-	public function getFirstRow($type = 'object')
+	public function getFirstRow(string $type = 'object')
 	{
 		$result = $this->getResult($type);
 
@@ -466,7 +466,7 @@ public function getFirstRow($type = 'object')
 	 *
 	 * @return mixed
 	 */
-	public function getLastRow($type = 'object')
+	public function getLastRow(string $type = 'object')
 	{
 		$result = $this->getResult($type);
 
@@ -482,7 +482,7 @@ public function getLastRow($type = 'object')
 	 *
 	 * @return mixed
 	 */
-	public function getNextRow($type = 'object')
+	public function getNextRow(string $type = 'object')
 	{
 		$result = $this->getResult($type);
 		if (empty($result))
@@ -502,7 +502,7 @@ public function getNextRow($type = 'object')
 	 *
 	 * @return mixed
 	 */
-	public function getPreviousRow($type = 'object')
+	public function getPreviousRow(string $type = 'object')
 	{
 		$result = $this->getResult($type);
 		if (empty($result))
@@ -527,7 +527,7 @@ public function getPreviousRow($type = 'object')
 	 *
 	 * @return mixed
 	 */
-	public function getUnbufferedRow($type = 'object')
+	public function getUnbufferedRow(string $type = 'object')
 	{
 		if ($type === 'array')
 		{
@@ -573,7 +573,7 @@ abstract public function getFieldData(): array;
 	/**
 	 * Frees the current result.
 	 *
-	 * @return mixed
+	 * @return void
 	 */
 	abstract public function freeResult();
 
@@ -588,7 +588,7 @@ abstract public function freeResult();
 	 *
 	 * @return mixed
 	 */
-	abstract public function dataSeek($n = 0);
+	abstract public function dataSeek(int $n = 0);
 
 	//--------------------------------------------------------------------
 
@@ -597,7 +597,7 @@ abstract public function dataSeek($n = 0);
 	 *
 	 * Overridden by driver classes.
 	 *
-	 * @return array
+	 * @return mixed
 	 */
 	abstract protected function fetchAssoc();
 
@@ -612,7 +612,7 @@ abstract protected function fetchAssoc();
 	 *
 	 * @return object
 	 */
-	abstract protected function fetchObject($className = 'stdClass');
+	abstract protected function fetchObject(string $className = 'stdClass');
 
 	//--------------------------------------------------------------------
 }
diff --git a/system/Database/BaseUtils.php b/system/Database/BaseUtils.php
index 096d1a1a5034..ce6f3bc1bedf 100644
--- a/system/Database/BaseUtils.php
+++ b/system/Database/BaseUtils.php
@@ -136,7 +136,7 @@ public function listDatabases()
 	 * @param  string $database_name
 	 * @return boolean
 	 */
-	public function databaseExists($database_name)
+	public function databaseExists(string $database_name): bool
 	{
 		return in_array($database_name, $this->listDatabases());
 	}
@@ -147,10 +147,10 @@ public function databaseExists($database_name)
 	 * Optimize Table
 	 *
 	 * @param  string $table_name
-	 * @return boolean|mixed
+	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function optimizeTable($table_name)
+	public function optimizeTable(string $table_name)
 	{
 		if ($this->optimizeTable === false)
 		{
@@ -231,7 +231,7 @@ public function optimizeDatabase()
 	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function repairTable($table_name)
+	public function repairTable(string $table_name)
 	{
 		if ($this->repairTable === false)
 		{
@@ -264,7 +264,7 @@ public function repairTable($table_name)
 	 *
 	 * @return string
 	 */
-	public function getCSVFromResult(ResultInterface $query, $delim = ',', $newline = "\n", $enclosure = '"')
+	public function getCSVFromResult(ResultInterface $query, string $delim = ',', string $newline = "\n", string $enclosure = '"')
 	{
 		$out = '';
 		// First generate the headings from the table column names
@@ -299,7 +299,7 @@ public function getCSVFromResult(ResultInterface $query, $delim = ',', $newline
 	 *
 	 * @return string
 	 */
-	public function getXMLFromResult(ResultInterface $query, $params = [])
+	public function getXMLFromResult(ResultInterface $query, array $params = []): string
 	{
 		// Set our default values
 		foreach (['root' => 'root', 'element' => 'element', 'newline' => "\n", 'tab' => "\t"] as $key => $val)
@@ -336,7 +336,7 @@ public function getXMLFromResult(ResultInterface $query, $params = [])
 	/**
 	 * Database Backup
 	 *
-	 * @param  array $params
+	 * @param  array|string $params
 	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
@@ -390,7 +390,7 @@ public function backup($params = [])
 		// Is the encoder supported? If not, we'll either issue an
 		// error or use plain text depending on the debug settings
 		if (($prefs['format'] === 'gzip' && ! function_exists('gzencode'))
-				|| ( $prefs['format'] === 'zip' && ! function_exists('gzcompress')))
+			|| ( $prefs['format'] === 'zip' && ! function_exists('gzcompress')))
 		{
 			if ($this->db->DBDebug)
 			{
@@ -407,7 +407,7 @@ public function backup($params = [])
 			if ($prefs['filename'] === '')
 			{
 				$prefs['filename'] = (count($prefs['tables']) === 1 ? $prefs['tables'] : $this->db->database)
-						. date('Y-m-d_H-i', time()) . '.sql';
+					. date('Y-m-d_H-i', time()) . '.sql';
 			}
 			else
 			{
diff --git a/system/Database/Config.php b/system/Database/Config.php
index f94c663ed7af..acd7f9ffb047 100644
--- a/system/Database/Config.php
+++ b/system/Database/Config.php
@@ -125,7 +125,7 @@ public static function connect($group = null, bool $getShared = true)
 	 *
 	 * @return array
 	 */
-	public static function getConnections()
+	public static function getConnections(): array
 	{
 		return static::$instances;
 	}
@@ -186,12 +186,12 @@ public static function seeder(string $group = null)
 	 */
 	protected static function ensureFactory()
 	{
-		if (static::$factory instanceof \CodeIgniter\Database\Database)
+		if (static::$factory instanceof Database)
 		{
 			return;
 		}
 
-		static::$factory = new \CodeIgniter\Database\Database();
+		static::$factory = new Database();
 	}
 
 	//--------------------------------------------------------------------
diff --git a/system/Database/ConnectionInterface.php b/system/Database/ConnectionInterface.php
index 76f8a64c3ac4..a4a9a2745046 100644
--- a/system/Database/ConnectionInterface.php
+++ b/system/Database/ConnectionInterface.php
@@ -61,7 +61,7 @@ public function initialize();
 	 * @param  boolean $persistent
 	 * @return mixed
 	 */
-	public function connect($persistent = false);
+	public function connect(bool $persistent = false);
 
 	//--------------------------------------------------------------------
 
@@ -130,18 +130,18 @@ public function getError();
 	/**
 	 * The name of the platform in use (MySQLi, mssql, etc)
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getPlatform();
+	public function getPlatform(): string;
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getVersion();
+	public function getVersion(): string;
 
 	//--------------------------------------------------------------------
 
@@ -154,7 +154,7 @@ public function getVersion();
 	 * queries if needed.
 	 *
 	 * @param string $sql
-	 * @param array  ...$binds
+	 * @param mixed  ...$binds
 	 *
 	 * @return mixed
 	 */
@@ -201,7 +201,7 @@ public function getLastQuery();
 	 * Escapes data based on type.
 	 * Sets boolean and null types.
 	 *
-	 * @param string $str
+	 * @param mixed $str
 	 *
 	 * @return mixed
 	 */
diff --git a/system/Database/Exceptions/DataException.php b/system/Database/Exceptions/DataException.php
index 966c6ef43f6f..2af1793454cc 100644
--- a/system/Database/Exceptions/DataException.php
+++ b/system/Database/Exceptions/DataException.php
@@ -1,4 +1,6 @@
-<?php namespace CodeIgniter\Database\Exceptions;
+<?php
+
+namespace CodeIgniter\Database\Exceptions;
 
 class DataException extends \RuntimeException implements ExceptionInterface
 {
@@ -51,12 +53,11 @@ public static function forTableNotFound(string $table)
 		return new static(lang('Database.tableNotFound', [$table]));
 	}
 
-
 	public static function forEmptyInputGiven(string $argument)
 	{
 		return new static(lang('Database.forEmptyInputGiven', [$argument]));
-  }
-  
+	}
+
 	public static function forFindColumnHaveMultipleColumns()
 	{
 		return new static(lang('Database.forFindColumnHaveMultipleColumns'));
diff --git a/system/Database/Migration.php b/system/Database/Migration.php
index eb27199dfd62..46b55a62b449 100644
--- a/system/Database/Migration.php
+++ b/system/Database/Migration.php
@@ -86,7 +86,7 @@ public function __construct(Forge $forge = null)
 	 *
 	 * @return string
 	 */
-	public function getDBGroup()
+	public function getDBGroup(): string
 	{
 		return $this->DBGroup;
 	}
diff --git a/system/Database/MigrationRunner.php b/system/Database/MigrationRunner.php
index 810e9a90791c..3a3604f86e5e 100644
--- a/system/Database/MigrationRunner.php
+++ b/system/Database/MigrationRunner.php
@@ -342,7 +342,7 @@ public function latest(string $namespace = null, string $group = null)
 	 *
 	 * @return boolean
 	 */
-	public function latestAll(string $group = null)
+	public function latestAll(string $group = null): bool
 	{
 		$this->ensureTable();
 
@@ -387,7 +387,7 @@ public function latestAll(string $group = null)
 	 *
 	 * @param string|null $group
 	 *
-	 * @return mixed    TRUE if no migrations are found, current version string on success, FALSE on failure
+	 * @return mixed    Current version string on success, FALSE on failure or no migrations are found
 	 */
 	public function current(string $group = null)
 	{
@@ -409,7 +409,7 @@ public function current(string $group = null)
 	 *
 	 * @return array    list of migrations as $version for one namespace
 	 */
-	public function findMigrations()
+	public function findMigrations(): array
 	{
 		$migrations = [];
 
@@ -471,11 +471,11 @@ public function findMigrations()
 	 *
 	 * @param array  $migrations
 	 * @param string $method
-	 * @param string $targetversion
+	 * @param string $targetVersion
 	 *
 	 * @return boolean
 	 */
-	protected function checkMigrations(array $migrations, string $method, string $targetversion)
+	protected function checkMigrations(array $migrations, string $method, string $targetVersion): bool
 	{
 		// Check if no migrations found
 		if (empty($migrations))
@@ -487,14 +487,14 @@ protected function checkMigrations(array $migrations, string $method, string $ta
 			throw new \RuntimeException(lang('Migrations.empty'));
 		}
 
-		// Check if $targetversion file is found
-		if ((int)$targetversion !== 0 && ! array_key_exists($targetversion, $migrations))
+		// Check if $targetVersion file is found
+		if ((int)$targetVersion !== 0 && ! array_key_exists($targetVersion, $migrations))
 		{
 			if ($this->silent)
 			{
 				return false;
 			}
-			throw new \RuntimeException(lang('Migrations.notFound') . $targetversion);
+			throw new \RuntimeException(lang('Migrations.notFound') . $targetVersion);
 		}
 
 		ksort($migrations);
@@ -601,7 +601,7 @@ public function setName(string $name)
 	 *
 	 * @return array
 	 */
-	public function getHistory(string $group = 'default')
+	public function getHistory(string $group = 'default'): array
 	{
 		$this->ensureTable();
 
@@ -645,7 +645,7 @@ public function setSilent(bool $silent)
 	 *
 	 * @return string    Numeric portion of a migration filename
 	 */
-	protected function getMigrationNumber(string $migration)
+	protected function getMigrationNumber(string $migration): string
 	{
 		return sscanf($migration, '%[0-9]+', $number) ? $number : '0';
 	}
@@ -659,7 +659,7 @@ protected function getMigrationNumber(string $migration)
 	 *
 	 * @return string    text portion of a migration filename
 	 */
-	protected function getMigrationName(string $migration)
+	protected function getMigrationName(string $migration): string
 	{
 		$parts = explode('_', $migration);
 		array_shift($parts);
@@ -674,7 +674,7 @@ protected function getMigrationName(string $migration)
 	 *
 	 * @return string    Current migration version
 	 */
-	protected function getVersion()
+	protected function getVersion(): string
 	{
 		$this->ensureTable();
 
@@ -695,7 +695,7 @@ protected function getVersion()
 	 *
 	 * @return array    Current migration version
 	 */
-	public function getCliMessages()
+	public function getCliMessages(): array
 	{
 		return $this->cliMessages;
 	}
@@ -708,6 +708,8 @@ public function getCliMessages()
 	 * @param string $version
 	 *
 	 * @internal param string $migration Migration reached
+	 *
+	 * @return void
 	 */
 	protected function addHistory(string $version)
 	{
@@ -731,6 +733,7 @@ protected function addHistory(string $version)
 	 * Removes a single history
 	 *
 	 * @param string $version
+	 * @return void
 	 */
 	protected function removeHistory(string $version)
 	{
diff --git a/system/Database/MySQLi/Connection.php b/system/Database/MySQLi/Connection.php
index 7c6d45c4909d..8d189e620448 100644
--- a/system/Database/MySQLi/Connection.php
+++ b/system/Database/MySQLi/Connection.php
@@ -89,7 +89,7 @@ class Connection extends BaseConnection implements ConnectionInterface
 	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function connect($persistent = false)
+	public function connect(bool $persistent = false)
 	{
 		// Do we have a socket path?
 		if ($this->hostname[0] === '/')
@@ -245,6 +245,8 @@ public function reconnect()
 
 	/**
 	 * Close the database connection.
+	 *
+	 * @return void
 	 */
 	protected function _close()
 	{
@@ -258,9 +260,9 @@ protected function _close()
 	 *
 	 * @param string $databaseName
 	 *
-	 * @return mixed
+	 * @return boolean
 	 */
-	public function setDatabase(string $databaseName)
+	public function setDatabase(string $databaseName): bool
 	{
 		if ($databaseName === '')
 		{
@@ -287,9 +289,9 @@ public function setDatabase(string $databaseName)
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getVersion()
+	public function getVersion(): string
 	{
 		if (isset($this->dataCache['version']))
 		{
@@ -313,7 +315,7 @@ public function getVersion()
 	 *
 	 * @return mixed
 	 */
-	public function execute($sql)
+	public function execute(string $sql)
 	{
 		while ($this->connID->more_results())
 		{
@@ -338,7 +340,7 @@ public function execute($sql)
 	 *
 	 * @return string
 	 */
-	protected function prepQuery($sql)
+	protected function prepQuery(string $sql): string
 	{
 		// mysqli_affected_rows() returns 0 for "DELETE FROM TABLE" queries. This hack
 		// modifies the query so that it a proper number of affected rows is returned.
@@ -355,7 +357,7 @@ protected function prepQuery($sql)
 	/**
 	 * Returns the total number of rows affected by this query.
 	 *
-	 * @return mixed
+	 * @return int
 	 */
 	public function affectedRows(): int
 	{
@@ -394,7 +396,7 @@ protected function _escapeString(string $str): string
 	 *
 	 * @return string
 	 */
-	protected function _listTables($prefixLimit = false): string
+	protected function _listTables(bool $prefixLimit = false): string
 	{
 		$sql = 'SHOW TABLES FROM ' . $this->escapeIdentifiers($this->database);
 
@@ -439,19 +441,19 @@ public function _fieldData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		for ($i = 0, $c = count($query); $i < $c; $i++)
 		{
-			$retval[$i]       = new \stdClass();
-			$retval[$i]->name = $query[$i]->Field;
+			$retVal[$i]       = new \stdClass();
+			$retVal[$i]->name = $query[$i]->Field;
 
-			sscanf($query[$i]->Type, '%[a-z](%d)', $retval[$i]->type, $retval[$i]->max_length);
+			sscanf($query[$i]->Type, '%[a-z](%d)', $retVal[$i]->type, $retVal[$i]->max_length);
 
-			$retval[$i]->default     = $query[$i]->Default;
-			$retval[$i]->primary_key = (int)($query[$i]->Key === 'PRI');
+			$retVal[$i]->default     = $query[$i]->Default;
+			$retVal[$i]->primary_key = (int)($query[$i]->Key === 'PRI');
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -550,7 +552,7 @@ public function _foreignKeyData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		foreach ($query as $row)
 		{
 			$obj                     = new \stdClass();
@@ -558,10 +560,10 @@ public function _foreignKeyData(string $table): array
 			$obj->table_name         = $row->TABLE_NAME;
 			$obj->foreign_table_name = $row->REFERENCED_TABLE_NAME;
 
-			$retval[] = $obj;
+			$retVal[] = $obj;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -575,7 +577,7 @@ public function _foreignKeyData(string $table): array
 	 *
 	 * @return array
 	 */
-	public function error()
+	public function error(): array
 	{
 		if (! empty($this->mysqli->connect_errno))
 		{
@@ -598,7 +600,7 @@ public function error()
 	 *
 	 * @return integer
 	 */
-	public function insertID()
+	public function insertID(): int
 	{
 		return $this->connID->insert_id;
 	}
diff --git a/system/Database/MySQLi/PreparedQuery.php b/system/Database/MySQLi/PreparedQuery.php
index 668df92ecfa3..89a339c2d2e9 100644
--- a/system/Database/MySQLi/PreparedQuery.php
+++ b/system/Database/MySQLi/PreparedQuery.php
@@ -80,9 +80,9 @@ public function _prepare(string $sql, array $options = [])
 	 *
 	 * @param array $data
 	 *
-	 * @return \CodeIgniter\Database\ResultInterface
+	 * @return bool
 	 */
-	public function _execute($data)
+	public function _execute(array $data): bool
 	{
 		if (is_null($this->statement))
 		{
diff --git a/system/Database/MySQLi/Result.php b/system/Database/MySQLi/Result.php
index 2906324e0927..5d66f86ec0e8 100644
--- a/system/Database/MySQLi/Result.php
+++ b/system/Database/MySQLi/Result.php
@@ -85,26 +85,28 @@ public function getFieldNames(): array
 	 */
 	public function getFieldData(): array
 	{
-		$retval    = [];
+		$retVal    = [];
 		$fieldData = $this->resultID->fetch_fields();
 
 		foreach ($fieldData as $i => $data)
 		{
-			$retval[$i]              = new \stdClass();
-			$retval[$i]->name        = $data->name;
-			$retval[$i]->type        = $data->type;
-			$retval[$i]->max_length  = $data->max_length;
-			$retval[$i]->primary_key = (int) ($data->flags & 2);
-			$retval[$i]->default     = $data->def;
+			$retVal[$i]              = new \stdClass();
+			$retVal[$i]->name        = $data->name;
+			$retVal[$i]->type        = $data->type;
+			$retVal[$i]->max_length  = $data->max_length;
+			$retVal[$i]->primary_key = (int) ($data->flags & 2);
+			$retVal[$i]->default     = $data->def;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Frees the current result.
+	 *
+	 * @return void
 	 */
 	public function freeResult()
 	{
@@ -126,7 +128,7 @@ public function freeResult()
 	 *
 	 * @return mixed
 	 */
-	public function dataSeek($n = 0)
+	public function dataSeek(int $n = 0)
 	{
 		return $this->resultID->data_seek($n);
 	}
@@ -138,7 +140,7 @@ public function dataSeek($n = 0)
 	 *
 	 * Overridden by driver classes.
 	 *
-	 * @return array
+	 * @return mixed
 	 */
 	protected function fetchAssoc()
 	{
@@ -156,7 +158,7 @@ protected function fetchAssoc()
 	 *
 	 * @return object
 	 */
-	protected function fetchObject($className = 'stdClass')
+	protected function fetchObject(string $className = 'stdClass')
 	{
 		return $this->resultID->fetch_object($className);
 	}
diff --git a/system/Database/MySQLi/Utils.php b/system/Database/MySQLi/Utils.php
index 25d4036e4e4d..2a6565c602ff 100644
--- a/system/Database/MySQLi/Utils.php
+++ b/system/Database/MySQLi/Utils.php
@@ -38,12 +38,13 @@
 
 namespace CodeIgniter\Database\MySQLi;
 
+use CodeIgniter\Database\BaseUtils;
 use CodeIgniter\Database\Exceptions\DatabaseException;
 
 /**
  * Utils for MySQLi
  */
-class Utils extends \CodeIgniter\Database\BaseUtils
+class Utils extends BaseUtils
 {
 
 	/**
diff --git a/system/Database/Postgre/Builder.php b/system/Database/Postgre/Builder.php
index 7ab065aa9992..df9104305c1f 100644
--- a/system/Database/Postgre/Builder.php
+++ b/system/Database/Postgre/Builder.php
@@ -53,7 +53,6 @@ class Builder extends BaseBuilder
 	 */
 	protected $randomKeyword = [
 		'RANDOM()',
-		'RANDOM()',
 	];
 
 	//--------------------------------------------------------------------
@@ -98,7 +97,7 @@ public function orderBy(string $orderBy, string $direction = '', bool $escape =
 	 * @param string  $column
 	 * @param integer $value
 	 *
-	 * @return boolean
+	 * @return mixed
 	 */
 	public function increment(string $column, int $value = 1)
 	{
@@ -117,7 +116,7 @@ public function increment(string $column, int $value = 1)
 	 * @param string  $column
 	 * @param integer $value
 	 *
-	 * @return boolean
+	 * @return mixed
 	 */
 	public function decrement(string $column, int $value = 1)
 	{
@@ -141,7 +140,7 @@ public function decrement(string $column, int $value = 1)
 	 * @param array   $set       An associative array of insert values
 	 * @param boolean $returnSQL
 	 *
-	 * @return   boolean TRUE on success, FALSE on failure
+	 * @return   mixed
 	 * @throws   DatabaseException
 	 * @internal param true $bool returns the generated SQL, false executes the query.
 	 */
diff --git a/system/Database/Postgre/Connection.php b/system/Database/Postgre/Connection.php
index 56aec4f905e0..eda14acc5dea 100644
--- a/system/Database/Postgre/Connection.php
+++ b/system/Database/Postgre/Connection.php
@@ -78,7 +78,7 @@ class Connection extends BaseConnection implements ConnectionInterface
 	 * @param  boolean $persistent
 	 * @return mixed
 	 */
-	public function connect($persistent = false)
+	public function connect(bool $persistent = false)
 	{
 		if (empty($this->DSN))
 		{
@@ -121,7 +121,7 @@ public function connect($persistent = false)
 	 * Keep or establish the connection if no queries have been sent for
 	 * a length of time exceeding the server's idle timeout.
 	 *
-	 * @return mixed
+	 * @return void
 	 */
 	public function reconnect()
 	{
@@ -135,6 +135,8 @@ public function reconnect()
 
 	/**
 	 * Close the database connection.
+	 *
+	 * @return void
 	 */
 	protected function _close()
 	{
@@ -148,9 +150,9 @@ protected function _close()
 	 *
 	 * @param string $databaseName
 	 *
-	 * @return mixed
+	 * @return boolean
 	 */
-	public function setDatabase(string $databaseName)
+	public function setDatabase(string $databaseName): bool
 	{
 		return false;
 	}
@@ -160,9 +162,9 @@ public function setDatabase(string $databaseName)
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getVersion()
+	public function getVersion(): string
 	{
 		if (isset($this->dataCache['version']))
 		{
@@ -186,7 +188,7 @@ public function getVersion()
 	 *
 	 * @return resource
 	 */
-	public function execute($sql)
+	public function execute(string $sql)
 	{
 		return pg_query($this->connID, $sql);
 	}
@@ -196,7 +198,7 @@ public function execute($sql)
 	/**
 	 * Returns the total number of rows affected by this query.
 	 *
-	 * @return mixed
+	 * @return int
 	 */
 	public function affectedRows(): int
 	{
@@ -210,7 +212,7 @@ public function affectedRows(): int
 	 *
 	 * Escapes data based on type
 	 *
-	 * @param  string $str
+	 * @param  mixed $str
 	 * @return mixed
 	 */
 	public function escape($str)
@@ -259,7 +261,7 @@ protected function _escapeString(string $str): string
 	 *
 	 * @return string
 	 */
-	protected function _listTables($prefixLimit = false): string
+	protected function _listTables(bool $prefixLimit = false): string
 	{
 		$sql = 'SELECT "table_name" FROM "information_schema"."tables" WHERE "table_schema" = \'' . $this->schema . "'";
 
@@ -312,17 +314,17 @@ public function _fieldData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		for ($i = 0, $c = count($query); $i < $c; $i ++)
 		{
-			$retval[$i]             = new \stdClass();
-			$retval[$i]->name       = $query[$i]->column_name;
-			$retval[$i]->type       = $query[$i]->data_type;
-			$retval[$i]->default    = $query[$i]->column_default;
-			$retval[$i]->max_length = $query[$i]->character_maximum_length > 0 ? $query[$i]->character_maximum_length : $query[$i]->numeric_precision;
+			$retVal[$i]             = new \stdClass();
+			$retVal[$i]->name       = $query[$i]->column_name;
+			$retVal[$i]->type       = $query[$i]->data_type;
+			$retVal[$i]->default    = $query[$i]->column_default;
+			$retVal[$i]->max_length = $query[$i]->character_maximum_length > 0 ? $query[$i]->character_maximum_length : $query[$i]->numeric_precision;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -347,7 +349,7 @@ public function _indexData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		foreach ($query as $row)
 		{
 			$obj         = new \stdClass();
@@ -366,10 +368,10 @@ public function _indexData(string $table): array
 				$obj->type = (strpos($row->indexdef, 'CREATE UNIQUE') === 0) ? 'UNIQUE' : 'INDEX';
 			}
 
-			$retval[$obj->name] = $obj;
+			$retVal[$obj->name] = $obj;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -401,17 +403,17 @@ public function _foreignKeyData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		foreach ($query as $row)
 		{
 			$obj                     = new \stdClass();
 			$obj->constraint_name    = $row->constraint_name;
 			$obj->table_name         = $row->table_name;
 			$obj->foreign_table_name = $row->foreign_table_name;
-			$retval[]                = $obj;
+			$retVal[]                = $obj;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -425,7 +427,7 @@ public function _foreignKeyData(string $table): array
 	 *
 	 * @return array
 	 */
-	public function error()
+	public function error(): array
 	{
 		return [
 			'code'    => '',
@@ -440,7 +442,7 @@ public function error()
 	 *
 	 * @return integer
 	 */
-	public function insertID()
+	public function insertID(): int
 	{
 		$v = pg_version($this->connID);
 		// 'server' key is only available since PostgreSQL 7.4
@@ -540,7 +542,7 @@ protected function buildDSN()
 	 * @param  string $charset The client encoding to which the data will be converted.
 	 * @return boolean
 	 */
-	protected function setClientEncoding($charset)
+	protected function setClientEncoding(string $charset): bool
 	{
 		return pg_set_client_encoding($this->connID, $charset) === 0;
 	}
diff --git a/system/Database/Postgre/PreparedQuery.php b/system/Database/Postgre/PreparedQuery.php
index fdd0aa4a07fd..6275ef96d844 100644
--- a/system/Database/Postgre/PreparedQuery.php
+++ b/system/Database/Postgre/PreparedQuery.php
@@ -74,6 +74,7 @@ class PreparedQuery extends BasePreparedQuery implements PreparedQueryInterface
 	 *                        Unused in the MySQLi driver.
 	 *
 	 * @return mixed
+	 * @throws \Exception
 	 */
 	public function _prepare(string $sql, array $options = [])
 	{
@@ -104,7 +105,7 @@ public function _prepare(string $sql, array $options = [])
 	 *
 	 * @return boolean
 	 */
-	public function _execute($data)
+	public function _execute(array $data): bool
 	{
 		if (is_null($this->statement))
 		{
diff --git a/system/Database/Postgre/Result.php b/system/Database/Postgre/Result.php
index af4af6682ad3..a6bde2419941 100644
--- a/system/Database/Postgre/Result.php
+++ b/system/Database/Postgre/Result.php
@@ -84,19 +84,19 @@ public function getFieldNames(): array
 	 */
 	public function getFieldData(): array
 	{
-		$retval = [];
+		$retVal = [];
 
 		for ($i = 0, $c = $this->getFieldCount(); $i < $c; $i ++)
 		{
-			$retval[$i]             = new \stdClass();
-			$retval[$i]->name       = pg_field_name($this->resultID, $i);
-			$retval[$i]->type       = pg_field_type($this->resultID, $i);
-			$retval[$i]->max_length = pg_field_size($this->resultID, $i);
-			// $retval[$i]->primary_key = (int)($fieldData[$i]->flags & 2);
-			// $retval[$i]->default     = $fieldData[$i]->def;
+			$retVal[$i]             = new \stdClass();
+			$retVal[$i]->name       = pg_field_name($this->resultID, $i);
+			$retVal[$i]->type       = pg_field_type($this->resultID, $i);
+			$retVal[$i]->max_length = pg_field_size($this->resultID, $i);
+			// $retVal[$i]->primary_key = (int)($fieldData[$i]->flags & 2);
+			// $retVal[$i]->default     = $fieldData[$i]->def;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -104,7 +104,7 @@ public function getFieldData(): array
 	/**
 	 * Frees the current result.
 	 *
-	 * @return mixed
+	 * @return void
 	 */
 	public function freeResult()
 	{
@@ -126,7 +126,7 @@ public function freeResult()
 	 *
 	 * @return mixed
 	 */
-	public function dataSeek($n = 0)
+	public function dataSeek(int $n = 0)
 	{
 		return pg_result_seek($this->resultID, $n);
 	}
@@ -138,7 +138,7 @@ public function dataSeek($n = 0)
 	 *
 	 * Overridden by driver classes.
 	 *
-	 * @return array
+	 * @return mixed
 	 */
 	protected function fetchAssoc()
 	{
@@ -156,7 +156,7 @@ protected function fetchAssoc()
 	 *
 	 * @return object
 	 */
-	protected function fetchObject($className = 'stdClass')
+	protected function fetchObject(string $className = 'stdClass')
 	{
 		return pg_fetch_object($this->resultID, null, $className);
 	}
diff --git a/system/Database/Postgre/Utils.php b/system/Database/Postgre/Utils.php
index 41143e7ecea6..846307c8a422 100644
--- a/system/Database/Postgre/Utils.php
+++ b/system/Database/Postgre/Utils.php
@@ -37,12 +37,13 @@
 
 namespace CodeIgniter\Database\Postgre;
 
+use CodeIgniter\Database\BaseUtils;
 use CodeIgniter\Database\Exceptions\DatabaseException;
 
 /**
  * Utils for Postgre
  */
-class Utils extends \CodeIgniter\Database\BaseUtils
+class Utils extends BaseUtils
 {
 
 	/**
diff --git a/system/Database/QueryInterface.php b/system/Database/QueryInterface.php
index 7f5cfb12879d..62450833a308 100644
--- a/system/Database/QueryInterface.php
+++ b/system/Database/QueryInterface.php
@@ -52,12 +52,13 @@ interface QueryInterface
 	/**
 	 * Sets the raw query string to use for this statement.
 	 *
-	 * @param string $sql
-	 * @param array  $binds
+	 * @param string  $sql
+	 * @param mixed   $binds
+	 * @param boolean $setEscape
 	 *
 	 * @return mixed
 	 */
-	public function setQuery(string $sql, $binds = null);
+	public function setQuery(string $sql, $binds = null, bool $setEscape = true);
 
 	//--------------------------------------------------------------------
 
@@ -91,9 +92,9 @@ public function setDuration(float $start, float $end = null);
 	 *
 	 * @param integer $decimals The accuracy of the returned time.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getDuration(int $decimals = 6);
+	public function getDuration(int $decimals = 6): string;
 
 	//--------------------------------------------------------------------
 
diff --git a/system/Database/ResultInterface.php b/system/Database/ResultInterface.php
index af217864fbe1..3fffd4265c1d 100644
--- a/system/Database/ResultInterface.php
+++ b/system/Database/ResultInterface.php
@@ -53,7 +53,7 @@ interface ResultInterface
 	 *
 	 * @return mixed
 	 */
-	public function getResult($type = 'object'): array;
+	public function getResult(string $type = 'object'): array;
 
 	//--------------------------------------------------------------------
 
@@ -96,12 +96,12 @@ public function getResultObject(): array;
 	 *
 	 * If row doesn't exist, returns null.
 	 *
-	 * @param integer $n    The index of the results to return
+	 * @param mixed   $n    The index of the results to return
 	 * @param string  $type The type of result object. 'array', 'object' or class name.
 	 *
 	 * @return mixed
 	 */
-	public function getRow($n = 0, $type = 'object');
+	public function getRow($n = 0, string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -115,7 +115,7 @@ public function getRow($n = 0, $type = 'object');
 	 *
 	 * @return mixed
 	 */
-	public function getCustomRowObject($n, string $className);
+	public function getCustomRowObject(int $n, string $className);
 
 	//--------------------------------------------------------------------
 
@@ -128,7 +128,7 @@ public function getCustomRowObject($n, string $className);
 	 *
 	 * @return mixed
 	 */
-	public function getRowArray($n = 0);
+	public function getRowArray(int $n = 0);
 
 	//--------------------------------------------------------------------
 
@@ -141,7 +141,7 @@ public function getRowArray($n = 0);
 	 *
 	 * @return mixed
 	 */
-	public function getRowObject($n = 0);
+	public function getRowObject(int $n = 0);
 
 	//--------------------------------------------------------------------
 
@@ -164,7 +164,7 @@ public function setRow($key, $value = null);
 	 *
 	 * @return mixed
 	 */
-	public function getFirstRow($type = 'object');
+	public function getFirstRow(string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -175,7 +175,7 @@ public function getFirstRow($type = 'object');
 	 *
 	 * @return mixed
 	 */
-	public function getLastRow($type = 'object');
+	public function getLastRow(string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -186,7 +186,7 @@ public function getLastRow($type = 'object');
 	 *
 	 * @return mixed
 	 */
-	public function getNextRow($type = 'object');
+	public function getNextRow(string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -197,7 +197,7 @@ public function getNextRow($type = 'object');
 	 *
 	 * @return mixed
 	 */
-	public function getPreviousRow($type = 'object');
+	public function getPreviousRow(string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -208,7 +208,7 @@ public function getPreviousRow($type = 'object');
 	 *
 	 * @return mixed
 	 */
-	public function getUnbufferedRow($type = 'object');
+	public function getUnbufferedRow(string $type = 'object');
 
 	//--------------------------------------------------------------------
 
@@ -242,7 +242,7 @@ public function getFieldData(): array;
 	/**
 	 * Frees the current result.
 	 *
-	 * @return mixed
+	 * @return void
 	 */
 	public function freeResult();
 
@@ -257,7 +257,7 @@ public function freeResult();
 	 *
 	 * @return mixed
 	 */
-	public function dataSeek($n = 0);
+	public function dataSeek(int $n = 0);
 
 	//--------------------------------------------------------------------
 }
diff --git a/system/Database/SQLite3/Connection.php b/system/Database/SQLite3/Connection.php
index 312c1ff408eb..2592ad85a2a3 100644
--- a/system/Database/SQLite3/Connection.php
+++ b/system/Database/SQLite3/Connection.php
@@ -76,7 +76,7 @@ class Connection extends BaseConnection implements ConnectionInterface
 	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function connect($persistent = false)
+	public function connect(bool $persistent = false)
 	{
 		if ($persistent && $this->db->DBDebug)
 		{
@@ -100,7 +100,7 @@ public function connect($persistent = false)
 	 * Keep or establish the connection if no queries have been sent for
 	 * a length of time exceeding the server's idle timeout.
 	 *
-	 * @return mixed
+	 * @return void
 	 */
 	public function reconnect()
 	{
@@ -127,9 +127,9 @@ protected function _close()
 	 *
 	 * @param string $databaseName
 	 *
-	 * @return mixed
+	 * @return boolean
 	 */
-	public function setDatabase(string $databaseName)
+	public function setDatabase(string $databaseName): bool
 	{
 		return false;
 	}
@@ -139,9 +139,9 @@ public function setDatabase(string $databaseName)
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getVersion()
+	public function getVersion(): string
 	{
 		if (isset($this->dataCache['version']))
 		{
@@ -162,7 +162,7 @@ public function getVersion()
 	 *
 	 * @return mixed    \SQLite3Result object or bool
 	 */
-	public function execute($sql)
+	public function execute(string $sql)
 	{
 		return $this->isWriteType($sql)
 			? $this->connID->exec($sql)
@@ -174,7 +174,7 @@ public function execute($sql)
 	/**
 	 * Returns the total number of rows affected by this query.
 	 *
-	 * @return mixed
+	 * @return int
 	 */
 	public function affectedRows(): int
 	{
@@ -204,7 +204,7 @@ protected function _escapeString(string $str): string
 	 *
 	 * @return string
 	 */
-	protected function _listTables($prefixLimit = false): string
+	protected function _listTables(bool $prefixLimit = false): string
 	{
 		return 'SELECT "NAME" FROM "SQLITE_MASTER" WHERE "TYPE" = \'table\''
 			   . (($prefixLimit !== false && $this->DBPrefix !== '')
@@ -235,7 +235,7 @@ protected function _listColumns(string $table = ''): string
 	 * @return array|false
 	 * @throws DatabaseException
 	 */
-	public function getFieldNames($table)
+	public function getFieldNames(string $table)
 	{
 		// Is there a cached result?
 		if (isset($this->dataCache['field_names'][$table]))
@@ -313,19 +313,19 @@ public function _fieldData(string $table): array
 		{
 			return [];
 		}
-		$retval = [];
+		$retVal = [];
 		for ($i = 0, $c = count($query); $i < $c; $i++)
 		{
-			$retval[$i]              = new \stdClass();
-			$retval[$i]->name        = $query[$i]->name;
-			$retval[$i]->type        = $query[$i]->type;
-			$retval[$i]->max_length  = null;
-			$retval[$i]->default     = $query[$i]->dflt_value;
-			$retval[$i]->primary_key = isset($query[$i]->pk) ? (bool)$query[$i]->pk : false;
-			$retval[$i]->nullable    = isset($query[$i]->notnull) ? ! (bool)$query[$i]->notnull : false;
+			$retVal[$i]              = new \stdClass();
+			$retVal[$i]->name        = $query[$i]->name;
+			$retVal[$i]->type        = $query[$i]->type;
+			$retVal[$i]->max_length  = null;
+			$retVal[$i]->default     = $query[$i]->dflt_value;
+			$retVal[$i]->primary_key = isset($query[$i]->pk) ? (bool)$query[$i]->pk : false;
+			$retVal[$i]->nullable    = isset($query[$i]->notnull) ? ! (bool)$query[$i]->notnull : false;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -348,7 +348,7 @@ public function _indexData(string $table): array
 		}
 		$query = $query->getResultObject();
 
-		$retval = [];
+		$retVal = [];
 		foreach ($query as $row)
 		{
 			$obj       = new \stdClass();
@@ -367,10 +367,10 @@ public function _indexData(string $table): array
 				$obj->fields[] = $field->name;
 			}
 
-			$retval[$obj->name] = $obj;
+			$retVal[$obj->name] = $obj;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -395,7 +395,7 @@ public function _foreignKeyData(string $table): array
 			return [];
 		}
 
-		$retval = [];
+		$retVal = [];
 
 		foreach ($tables as $table)
 		{
@@ -408,11 +408,11 @@ public function _foreignKeyData(string $table): array
 				$obj->table_name         = $table;
 				$obj->foreign_table_name = $row->table;
 
-				$retval[] = $obj;
+				$retVal[] = $obj;
 			}
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
diff --git a/system/Database/SQLite3/PreparedQuery.php b/system/Database/SQLite3/PreparedQuery.php
index 50e8deed9fb9..9f9848db8807 100644
--- a/system/Database/SQLite3/PreparedQuery.php
+++ b/system/Database/SQLite3/PreparedQuery.php
@@ -89,7 +89,7 @@ public function _prepare(string $sql, array $options = [])
 	 *
 	 * @return boolean
 	 */
-	public function _execute($data)
+	public function _execute(array $data): bool
 	{
 		if (is_null($this->statement))
 		{
diff --git a/system/Database/SQLite3/Result.php b/system/Database/SQLite3/Result.php
index 8a912bdec366..d1e22ca29452 100644
--- a/system/Database/SQLite3/Result.php
+++ b/system/Database/SQLite3/Result.php
@@ -92,18 +92,18 @@ public function getFieldData(): array
 			SQLITE3_NULL    => 'null',
 		];
 
-		$retval = [];
+		$retVal = [];
 
 		for ($i = 0, $c = $this->getFieldCount(); $i < $c; $i ++)
 		{
-			$retval[$i]             = new \stdClass();
-			$retval[$i]->name       = $this->resultID->columnName($i);
+			$retVal[$i]             = new \stdClass();
+			$retVal[$i]->name       = $this->resultID->columnName($i);
 			$type                   = $this->resultID->columnType($i);
-			$retval[$i]->type       = isset($data_types[$type]) ? $data_types[$type] : $type;
-			$retval[$i]->max_length = null;
+			$retVal[$i]->type       = isset($data_types[$type]) ? $data_types[$type] : $type;
+			$retVal[$i]->max_length = null;
 		}
 
-		return $retval;
+		return $retVal;
 	}
 
 	//--------------------------------------------------------------------
@@ -134,7 +134,7 @@ public function freeResult()
 	 * @return mixed
 	 * @throws \CodeIgniter\Database\Exceptions\DatabaseException
 	 */
-	public function dataSeek($n = 0)
+	public function dataSeek(int $n = 0)
 	{
 		if ($n !== 0)
 		{
@@ -151,7 +151,7 @@ public function dataSeek($n = 0)
 	 *
 	 * Overridden by driver classes.
 	 *
-	 * @return array
+	 * @return mixed
 	 */
 	protected function fetchAssoc()
 	{
@@ -167,9 +167,9 @@ protected function fetchAssoc()
 	 *
 	 * @param string $className
 	 *
-	 * @return object
+	 * @return object|boolean
 	 */
-	protected function fetchObject($className = 'stdClass')
+	protected function fetchObject(string $className = 'stdClass')
 	{
 		// No native support for fetching rows as objects
 		if (($row = $this->fetchAssoc()) === false)
diff --git a/system/Database/SQLite3/Table.php b/system/Database/SQLite3/Table.php
index 0b31eb4ef955..e1332aeb5d56 100644
--- a/system/Database/SQLite3/Table.php
+++ b/system/Database/SQLite3/Table.php
@@ -214,6 +214,8 @@ public function modifyColumn(array $field)
 
 	/**
 	 * Creates the new table based on our current fields.
+	 *
+	 * @return mixed
 	 */
 	protected function createTable()
 	{
@@ -264,6 +266,8 @@ protected function createTable()
 	 * Copies data from our old table to the new one,
 	 * taking care map data correctly based on any columns
 	 * that have been renamed.
+	 *
+	 * @return void
 	 */
 	protected function copyData()
 	{
@@ -297,7 +301,7 @@ protected function copyData()
 	 *
 	 * @param array|boolean $fields
 	 *
-	 * @return array
+	 * @return mixed
 	 */
 	protected function formatFields($fields)
 	{
@@ -332,7 +336,7 @@ protected function formatFields($fields)
 	 * Converts keys retrieved from the database to
 	 * the format needed to create later.
 	 *
-	 * @param $keys
+	 * @param mixed $keys
 	 *
 	 * @return mixed
 	 */
@@ -359,6 +363,8 @@ protected function formatKeys($keys)
 	/**
 	 * Attempts to drop all indexes and constraints
 	 * from the database for this table.
+	 *
+	 * @return null|void
 	 */
 	protected function dropIndexes()
 	{
diff --git a/system/Database/SQLite3/Utils.php b/system/Database/SQLite3/Utils.php
index bdb8ec0ded66..ec16479f84a3 100644
--- a/system/Database/SQLite3/Utils.php
+++ b/system/Database/SQLite3/Utils.php
@@ -38,12 +38,13 @@
 
 namespace CodeIgniter\Database\SQLite3;
 
+use CodeIgniter\Database\BaseUtils;
 use CodeIgniter\Database\Exceptions\DatabaseException;
 
 /**
  * Utils for SQLite3
  */
-class Utils extends \CodeIgniter\Database\BaseUtils
+class Utils extends BaseUtils
 {
 
 	/**
diff --git a/tests/_support/Database/MockConnection.php b/tests/_support/Database/MockConnection.php
index e78405336187..699595bbfc3a 100644
--- a/tests/_support/Database/MockConnection.php
+++ b/tests/_support/Database/MockConnection.php
@@ -1,5 +1,6 @@
 <?php namespace Tests\Support\Database;
 
+use CodeIgniter\CodeIgniter;
 use CodeIgniter\Database\BaseConnection;
 
 class MockConnection extends BaseConnection
@@ -21,7 +22,23 @@ public function shouldReturn(string $method, $return)
 
 	//--------------------------------------------------------------------
 
-	public function query(string $sql, $binds = null, bool $setEscapeFlags = true, $queryClass = 'CodeIgniter\\Database\\Query')
+	/**
+	 * Orchestrates a query against the database. Queries must use
+	 * Database\Statement objects to store the query and build it.
+	 * This method works with the cache.
+	 *
+	 * Should automatically handle different connections for read/write
+	 * queries if needed.
+	 *
+	 * @param string  $sql
+	 * @param mixed   ...$binds
+	 * @param boolean $setEscapeFlags
+	 * @param string  $queryClass
+	 *
+	 * @return \CodeIgniter\Database\BaseResult|\CodeIgniter\Database\Query|false
+	 */
+
+	public function query(string $sql, $binds = null, bool $setEscapeFlags = true, string $queryClass = 'CodeIgniter\\Database\\Query')
 	{
 		$queryClass = str_replace('Connection', 'Query', get_class($this));
 
@@ -60,9 +77,11 @@ public function query(string $sql, $binds = null, bool $setEscapeFlags = true, $
 	/**
 	 * Connect to the database.
 	 *
+	 * @param boolean $persistent
+	 *
 	 * @return mixed
 	 */
-	public function connect($persistent = false)
+	public function connect(bool $persistent = false)
 	{
 		$return = $this->returnValues['connect'] ?? true;
 
@@ -82,9 +101,9 @@ public function connect($persistent = false)
 	 * Keep or establish the connection if no queries have been sent for
 	 * a length of time exceeding the server's idle timeout.
 	 *
-	 * @return mixed
+	 * @return boolean
 	 */
-	public function reconnect()
+	public function reconnect(): bool
 	{
 		return true;
 	}
@@ -110,11 +129,11 @@ public function setDatabase(string $databaseName)
 	/**
 	 * Returns a string containing the version of the database being used.
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getVersion()
+	public function getVersion(): string
 	{
-		return \CodeIgniter\CodeIgniter::CI_VERSION;
+		return CodeIgniter::CI_VERSION;
 	}
 
 	//--------------------------------------------------------------------
@@ -122,11 +141,11 @@ public function getVersion()
 	/**
 	 * Executes the query against the database.
 	 *
-	 * @param $sql
+	 * @param string    $sql
 	 *
 	 * @return mixed
 	 */
-	protected function execute($sql)
+	protected function execute(string $sql)
 	{
 		return $this->returnValues['execute'];
 	}
@@ -136,7 +155,7 @@ protected function execute($sql)
 	/**
 	 * Returns the total number of rows affected by this query.
 	 *
-	 * @return mixed
+	 * @return int
 	 */
 	public function affectedRows(): int
 	{
@@ -154,7 +173,7 @@ public function affectedRows(): int
 	 *
 	 * @return array
 	 */
-	public function error()
+	public function error(): array
 	{
 		return [
 			'code'    => null,
@@ -169,7 +188,7 @@ public function error()
 	 *
 	 * @return integer
 	 */
-	public function insertID()
+	public function insertID(): int
 	{
 		return $this->connID->insert_id;
 	}
@@ -183,7 +202,7 @@ public function insertID()
 	 *
 	 * @return string
 	 */
-	protected function _listTables($constrainByPrefix = false): string
+	protected function _listTables(bool $constrainByPrefix = false): string
 	{
 		return '';
 	}
diff --git a/tests/_support/Database/MockResult.php b/tests/_support/Database/MockResult.php
index d33207ff0464..dfe97a99fd5b 100644
--- a/tests/_support/Database/MockResult.php
+++ b/tests/_support/Database/MockResult.php
@@ -68,9 +68,9 @@ public function dataSeek($n = 0)
 	 *
 	 * Overridden by driver classes.
 	 *
-	 * @return array
+	 * @return mixed
 	 */
-	protected function fetchAssoc(): array
+	protected function fetchAssoc()
 	{
 	}