index.php

<?php

// Check PHP version.
$minPhpVersion = '7.4'; // If you update this, don't forget to update `spark`.
if (version_compare(PHP_VERSION, $minPhpVersion, '<')) {
    $message = sprintf(
        'Your PHP version must be %s or higher to run CodeIgniter. Current version: %s',
        $minPhpVersion,
        PHP_VERSION
    );

    exit($message);
}

// Path to the front controller (this file)
define('FCPATH', __DIR__ . DIRECTORY_SEPARATOR);

// Ensure the current directory is pointing to the front controller's directory
chdir(FCPATH);

/*
 *---------------------------------------------------------------
 * BOOTSTRAP THE APPLICATION
 *---------------------------------------------------------------
 * This process sets up the path constants, loads and registers
 * our autoloader, along with Composer's, loads our constants
 * and fires up an environment-specific bootstrapping.
 */

// Load our paths config file
// This is the line that might need to be changed, depending on your folder structure.
require FCPATH . 'app/Config/Paths.php';
// ^^^ Change this line if you move your application folder

$paths = new Config\Paths();

// Location of the framework bootstrap file.
require rtrim($paths->systemDirectory, '\\/ ') . DIRECTORY_SEPARATOR . 'bootstrap.php';

// Load environment settings from .env files into $_SERVER and $_ENV
require_once SYSTEMPATH . 'Config/DotEnv.php';
(new CodeIgniter\Config\DotEnv(ROOTPATH))->load();

/*
 * ---------------------------------------------------------------
 * GRAB OUR CODEIGNITER INSTANCE
 * ---------------------------------------------------------------
 *
 * The CodeIgniter class contains the core functionality to make
 * the application run, and does all the dirty work to get
 * the pieces all working together.
 */

$app = Config\Services::codeigniter();
$app->initialize();
$context = is_cli() ? 'php-cli' : 'web';
$app->setContext($context);

$dbArray = new \Config\Database();
if (!empty($dbArray) && !empty($dbArray->default)) {
    if (empty($dbArray->default['database']) || empty($dbArray->default['username'])) {
        $root = (isset($_SERVER['HTTPS']) ? "https://" : "http://") . $_SERVER['HTTP_HOST'];
        $root .= str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);
        header('Location: ' . $root . 'install/welcome.php');
        exit();
    }
}

/*
 *---------------------------------------------------------------
 * LAUNCH THE APPLICATION
 *---------------------------------------------------------------
 * Now that everything is set up, it's time to actually fire
 * up the engines and make this app do its thang.
 */

$app->run();