diff --git a/system/Cache/Handlers/FileHandler.php b/system/Cache/Handlers/FileHandler.php
index a86a45e83d00..fd0630a9982c 100644
--- a/system/Cache/Handlers/FileHandler.php
+++ b/system/Cache/Handlers/FileHandler.php
@@ -337,13 +337,13 @@ protected function getDirFileInfo(string $sourceDir, bool $topLevelOnly = true,
         $relativePath     = $sourceDir;
 
         if ($fp = @opendir($sourceDir)) {
-            // reset the array and make sure $source_dir has a trailing slash on the initial call
+            // reset the array and make sure $sourceDir has a trailing slash on the initial call
             if ($_recursion === false) {
                 $_filedata = [];
                 $sourceDir = rtrim(realpath($sourceDir) ?: $sourceDir, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
             }
 
-            // Used to be foreach (scandir($source_dir, 1) as $file), but scandir() is simply not as fast
+            // Used to be foreach (scandir($sourceDir, 1) as $file), but scandir() is simply not as fast
             while (false !== ($file = readdir($fp))) {
                 if (is_dir($sourceDir . $file) && $file[0] !== '.' && $topLevelOnly === false) {
                     $this->getDirFileInfo($sourceDir . $file . DIRECTORY_SEPARATOR, $topLevelOnly, true);
diff --git a/system/Database/BaseConnection.php b/system/Database/BaseConnection.php
index 0a88b00a4445..464791df2aaf 100644
--- a/system/Database/BaseConnection.php
+++ b/system/Database/BaseConnection.php
@@ -406,7 +406,7 @@ public function initialize()
         /* If an established connection is available, then there's
          * no need to connect and select the database.
          *
-         * Depending on the database driver, conn_id can be either
+         * Depending on the database driver, connID can be either
          * boolean TRUE, a resource or an object.
          */
         if ($this->connID) {
@@ -846,7 +846,7 @@ public function transBegin(bool $testMode = false): bool
         }
 
         // Reset the transaction failure flag.
-        // If the $test_mode flag is set to TRUE transactions will be rolled back
+        // If the $testMode flag is set to TRUE transactions will be rolled back
         // even if the queries produce a successful result.
         $this->transFailure = $testMode;
 
diff --git a/system/Database/MySQLi/Connection.php b/system/Database/MySQLi/Connection.php
index f62a27a7d200..b40db946894d 100644
--- a/system/Database/MySQLi/Connection.php
+++ b/system/Database/MySQLi/Connection.php
@@ -57,7 +57,7 @@ class Connection extends BaseConnection
     /**
      * MySQLi object
      *
-     * Has to be preserved without being assigned to $conn_id.
+     * Has to be preserved without being assigned to $connId.
      *
      * @var false|mysqli
      */
diff --git a/system/Helpers/filesystem_helper.php b/system/Helpers/filesystem_helper.php
index 2b86654c960e..4b0b49be6464 100644
--- a/system/Helpers/filesystem_helper.php
+++ b/system/Helpers/filesystem_helper.php
@@ -260,13 +260,13 @@ function get_dir_file_info(string $sourceDir, bool $topLevelOnly = true, bool $r
         try {
             $fp = opendir($sourceDir);
 
-            // reset the array and make sure $source_dir has a trailing slash on the initial call
+            // reset the array and make sure $sourceDir has a trailing slash on the initial call
             if ($recursion === false) {
                 $fileData  = [];
                 $sourceDir = rtrim(realpath($sourceDir), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
             }
 
-            // Used to be foreach (scandir($source_dir, 1) as $file), but scandir() is simply not as fast
+            // Used to be foreach (scandir($sourceDir, 1) as $file), but scandir() is simply not as fast
             while (false !== ($file = readdir($fp))) {
                 if (is_dir($sourceDir . $file) && $file[0] !== '.' && $topLevelOnly === false) {
                     get_dir_file_info($sourceDir . $file . DIRECTORY_SEPARATOR, $topLevelOnly, true);
diff --git a/system/Security/Security.php b/system/Security/Security.php
index 4d4d856cc1d8..b6d2660295b9 100644
--- a/system/Security/Security.php
+++ b/system/Security/Security.php
@@ -422,7 +422,7 @@ public function shouldRedirect(): bool
      *
      * If it is acceptable for the user input to include relative paths,
      * e.g. file/in/some/approved/folder.txt, you can set the second optional
-     * parameter, $relative_path to TRUE.
+     * parameter, $relativePath to TRUE.
      *
      * @param string $str          Input file name
      * @param bool   $relativePath Whether to preserve paths
diff --git a/system/Security/SecurityInterface.php b/system/Security/SecurityInterface.php
index 1460cf0e6a00..03a5ba2321d0 100644
--- a/system/Security/SecurityInterface.php
+++ b/system/Security/SecurityInterface.php
@@ -64,7 +64,7 @@ public function shouldRedirect(): bool;
      *
      * If it is acceptable for the user input to include relative paths,
      * e.g. file/in/some/approved/folder.txt, you can set the second optional
-     * parameter, $relative_path to TRUE.
+     * parameter, $relativePath to TRUE.
      *
      * @param string $str          Input file name
      * @param bool   $relativePath Whether to preserve paths