Default approach to extending class

class WC_Product(){
	function __construct( $product ){
		// main class stuff
	}
}

class WC_Product_Simple extends WC_Product() {
	function __construct( $product ){
		parent::__construct( $product );
	}
}

class WC_Product_NYP_Simple extends WC_Product_Simple() {
	function __construct( $product ){
		parent::__construct( $product );
	}

	function nyp_method(){
	// something NYP specific
	}

}