WP_Widget_Factory

class WP_Widget_Factory {

	/**
	 * Widgets array.
	 *
	 * @since WP-2.8.0
	 * @var array
	 */
	public $widgets = array();

	/**
	 * PHP5 constructor.
	 *
	 * @since WP-4.3.0
	 */
	public function __construct() {
		add_action( 'widgets_init', array( $this, '_register_widgets' ), 100 );
	}

	/**
	 * PHP4 constructor.
	 *
	 * @since WP-2.8.0
	 */
	public function WP_Widget_Factory() {
		_deprecated_constructor( 'WP_Widget_Factory', 'WP-4.2.0' );
		self::__construct();
	}

	/**
	 * Memory for the number of times unique class instances have been hashed.
	 *
	 * This can be eliminated in favor of straight spl_object_hash() when 5.3
	 * is the minimum requirement for PHP.
	 *
	 * @since WP-4.6.0
	 * @var array
	 *
	 * @see WP_Widget_Factory::hash_object()
	 */
	private $hashed_class_counts = array();

	/**
	 * Hashes an object, doing fallback of `spl_object_hash()` if not available.
	 *
	 * This can be eliminated in favor of straight spl_object_hash() when 5.3
	 * is the minimum requirement for PHP.
	 *
	 * @since WP-4.6.0
	 *
	 * @param WP_Widget $widget Widget.
	 * @return string Object hash.
	 */
	private function hash_object( $widget ) {
		if ( function_exists( 'spl_object_hash' ) ) {
			return spl_object_hash( $widget );
		} else {
			$class_name = get_class( $widget );
			$hash = $class_name;
			if ( ! isset( $widget->_wp_widget_factory_hash_id ) ) {
				if ( ! isset( $this->hashed_class_counts[ $class_name ] ) ) {
					$this->hashed_class_counts[ $class_name ] = 0;
				}
				$this->hashed_class_counts[ $class_name ] += 1;
				$widget->_wp_widget_factory_hash_id = $this->hashed_class_counts[ $class_name ];
			}
			$hash .= ':' . $widget->_wp_widget_factory_hash_id;
			return $hash;
		}
	}

	/**
	 * Registers a widget subclass.
	 *
	 * @since WP-2.8.0
	 * @since WP-4.6.0 Updated the `$widget` parameter to also accept a WP_Widget instance object
	 *              instead of simply a `WP_Widget` subclass name.
	 *
	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
	 */
	public function register( $widget ) {
		if ( $widget instanceof WP_Widget ) {
			$this->widgets[ $this->hash_object( $widget ) ] = $widget;
		} else {
			$this->widgets[ $widget ] = new $widget();
		}
	}

	/**
	 * Un-registers a widget subclass.
	 *
	 * @since WP-2.8.0
	 * @since WP-4.6.0 Updated the `$widget` parameter to also accept a WP_Widget instance object
	 *              instead of simply a `WP_Widget` subclass name.
	 *
	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
	 */
	public function unregister( $widget ) {
		if ( $widget instanceof WP_Widget ) {
			unset( $this->widgets[ $this->hash_object( $widget ) ] );
		} else {
			unset( $this->widgets[ $widget ] );
		}
	}

	/**
	 * Serves as a utility method for adding widgets to the registered widgets global.
	 *
	 * @since WP-2.8.0
	 *
	 * @global array $wp_registered_widgets
	 */
	public function _register_widgets() {
		global $wp_registered_widgets;
		$keys = array_keys($this->widgets);
		$registered = array_keys($wp_registered_widgets);
		$registered = array_map('_get_widget_id_base', $registered);

		foreach ( $keys as $key ) {
			// don't register new widget if old widget with the same id is already registered
			if ( in_array($this->widgets[$key]->id_base, $registered, true) ) {
				unset($this->widgets[$key]);
				continue;
			}

			$this->widgets[$key]->_register();
		}
	}
}