protected function defineId($app_name, $ext_name)
	{
		$ext_callable = function ($id) {
			return empty($id) ? null : new MongoId($id);
		};

		$this->define($app_name, $ext_name, 'strval', $ext_callable);
	}
protected function defineId($app_name, $ext_name)
	{
		$ext_callable = function ($id) {
			return empty($id) ? null : new MongoId($id);
		};

		$this->define($app_name, $ext_name, 'strval', $ext_callable);
	}
protected function defineId ( $ app_name , $ ext_name ) { $ ext_callable = function ( $ id ) { return empty ( $ id ) ? null : new MongoId ( $ id ) ; } ; $ this -> define ( $ app_name , $ ext_name , 'strval' , $ ext_callable ) ; }
Defines an ID property.

@param string $app_name Property name in application context.
@param string $ext_name Property name storage context.
Defines an ID property .