Autoload classes, interfaces and traits by namespace prefix

class-autoload.php

<?php
/**
 * Autoload classes, interfaces and traits for your namespaces.
 *
 * @package Autoload
 */

/**
 * Class Autoload
 */
class Autoload {

	/**
	 * Classmap file
	 *
	 * @var string
	 */
	private $map_file;
	/**
	 * Classmap
	 *
	 * @var array
	 */
	private $map;
	/**
	 * Prefix for your namespace
	 *
	 * @var string
	 */
	private $prefix = 'Custom_';
	/**
	 * Has the cache been updated
	 *
	 * @var bool
	 */
	private $has_been_update = false;

	/**
	 * Autoload constructor.
	 *
	 * @throws Exception Class|Interface|Trait not found.
	 */
	public function __construct() {
		$this->map_file = __DIR__ . '/classmap.php';
		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
		$this->map = @include $this->map_file;
		$this->map = is_array( $this->map ) ? $this->map : [];
		spl_autoload_register( [ $this, 'autoload' ] );
		add_action( 'shutdown', [ $this, 'update_cache' ] );
	}

	/**
	 * Autoload files for custom plugins
	 *
	 * @param string $class Full class name.
	 */
	private function autoload( string $class ): void {
		if ( 0 === strpos( $class, $this->prefix ) ) {
			if ( $this->map[ $class ] && file_exists( $this->map[ $class ] ) ) {
				require_once $this->map[ $class ];
			} else {
				$this->has_been_update = true;
				$plugin_parts          = explode( '\\', $class );
				$name                  = array_pop( $plugin_parts );
				$name                  = preg_match( '/^(Interface|Trait)/', $name )
					? $name . '.php'
					: 'class-' . $name . '.php';
				$path                  = implode( '/', $plugin_parts ) . '/' . $name;
				$path                  = strtolower( str_replace( [ '\\', '_' ], [ '/', '-' ], $path ) );
				$path                  = WP_CONTENT_DIR . '/plugins/' . $path;
				// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
				$this->map[ $class ] = $path;
				require_once $path;
			}
		}
	}

	/**
	 * Create instance WP_Filesystem
	 *
	 * @return WP_Filesystem_Direct
	 *
	 * phpcs:disable WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
	 */
	private function WP_Filesystem(): WP_Filesystem_Direct {
		//phpcs:enable WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
		global $wp_filesystem;
		if ( null === $wp_filesystem ) {
			if ( ! class_exists( 'WP_Filesystem_Base' ) ) {
				require_once ABSPATH . 'wp-admin/includes/file.php';
				require_once ABSPATH . 'wp-admin/includes/class-wp-filesystem-base.php';
				require_once ABSPATH . 'wp-admin/includes/class-wp-filesystem-direct.php';
			}
			WP_Filesystem();
		}

		return new WP_Filesystem_Direct( null );
	}

	/**
	 * Update classmap
	 */
	public function update_cache(): void {
		if ( ! $this->has_been_update ) {
			return;
		}
		$map = implode(
			"\n",
			array_map(
				function ( $k, $v ) {
					return "'$k' => '$v',";
				},
				array_keys( $this->map ),
				array_values( $this->map )
			)
		);
		// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_read_file_put_contents
		$filesystem = self::WP_Filesystem();
		$filesystem->put_contents( $this->map_file, '<?php return [' . $map . '];' );
	}

}