adapter

// v1
class HwLib {


    function hello() {
        return "hello";
    }


    function world() {
        return "world";
    }
}
*/
// v2
class HwLib {


    function greet() {
        return "greetings and salutations";
    }


    function world() {
        return "world";
    }
}


class HwLibV2ToV1Adapter {
    public $libv2;


    function __construct($libv2) {
        $this->libv2 = $libv2;
    }


    function hello() {
        return $this->libv2->greet();
    }


    function world() {
        return "world";
    }
}




//the original application call didn’t pass a parameter, the HwLibInstance() Factory defaults to returning
//an instance of the HwLib wrapped in the HwLibV2toV1Adapter class. However, if you’re writing new
//code, you can pass in a parameter of ‘V2’ to let the function know you want the HwLib newer version
//directly without adapting it.
function HwLibInstance($ver = false) {
    switch ($ver) {
        case 'V2'' :
            return new HwLib();
        default :
            return new HwLibV2ToV1Adapter(new HwLib());
    }
}