A Simple PHP Class for Autoloading

AutoLoader.php

<?php
/**
 * AutoLoader.php
 */
declare(strict_types=1);

namespace Autoloader;

/**
 * Autoloader class for automatically loading PHP classes based on namespaces.
 */
class AutoLoader
{
    /**
     * File extension for PHP class files.
     */
    private const EXT = '.php';

    /**
     * Load a class file based on its namespace.
     *
     * @param string $className The fully qualified class name (with namespace).
     * @return void
     */
    private static function loadClass(string $className): void
    {
        // Split the class name into namespace segments.
        $namespaceSegments = explode('\\', $className);

        // Get the class file name.
        $fileName = end($namespaceSegments);

        // Remove the class name from the segments array.
        array_pop($namespaceSegments);

        // Construct the relative file path.
        $relativePath = implode(DIRECTORY_SEPARATOR, array_map('trim', $namespaceSegments));

        // Get the absolute path to the class file.
        $absolutePath = realpath($relativePath);

        // Construct the full path to the class file.
        $fullPath = $absolutePath . DIRECTORY_SEPARATOR . $fileName . self::EXT;

        try {
            // Check if the class file exists and require it.
            if (file_exists($fullPath)) {
                require_once $fullPath;
            } else {
                // Handle the case where the class file does not exist.
                throw new \RuntimeException("Class file not found: $className");
            }
        } catch (\RuntimeException $e) {
            // Handle the exception (e.g., log the error or display an error message).
            // You can customize the error handling here.
            echo 'Autoloader Error: ' . $e->getMessage();
            // Optionally, you can also re-throw the exception to propagate it further.
            // throw $e;
        }
    }

    /**
     * Register the autoloader with spl_autoload_register().
     *
     * @return void
     */
    public static function register(): void
    {
        spl_autoload_register([self::class, 'loadClass']);
    }

    /**
     * Unregister the autoloader with spl_autoload_unregister().
     *
     * @return void
     */
    public static function unregister(): void
    {
        spl_autoload_unregister([self::class, 'loadClass']);
    }
}

// Register the autoloader when AutoLoader.php is included.
AutoLoader::register();