Question

I was trying to find a way to execute some code to alter the results of an objects methods without actually touching the object’s code. One way I came up is using a decorator:

class Decorator {
    private $object;

    public function __construct($object) {
        if (!is_object($object)) {
            throw new Exception("Not an object");
        }
        $this->object = $object;
    }

    protected function doSomething(&$val) {
        $val .= "!!";
    }

    public function __call($name, $arguments) {
        $retVal = call_user_func_array(array($this->object, $name), $arguments);
        $this->doSomething($retVal);
        return $retVal;
    }
}

class Test extends BaseTest {
    public function run() {
        return "Test->run()";
    }
}

$o = new Decorator(new Test());
$o->run();

That way it will work properly but it has one disadvantage which makes it unusable for me right now – it would require replacing all lines with new Test() with new Decorator(new Test()) and this is exactly what I would like to avoid – lots of meddling with the existing code. Maybe something I could do in the base class?

Answer 1

One does not simply overload stuff in PHP. So what you want cannot be done. But the fact that you are in trouble now is a big tell your design is flawed. Or if it is not your code design the code you have to work with (I feel your pain).

If you cannot do what you want to do it is because you have tightly coupled your code. I.e. you make use of the new keyword in classes instead of injecting them (dependency injection) into the classes / methods that need it.

Besides not being able to easily swap classes you would also have a gard time easily testing your units because of the tight coupling.

UPDATE

For completeness (for possible future readers): if the specific class would have been namespaced and you were allowed to change the namespace you could have thought about changing the namespace. However this is not really good practice, because it may screw with for example autoloaders. An example of this would be PSR-0. But considering you cannot do this either way I don’t see it is possible what you want. P.S. you should not really use this “solution”.

UPDATE2

It looks like there has been some overload extension at some time (way way way back), but the only thing I have found about it is some bug report. And don’t count on it still working now either way. 😉 There simply is no real overloading in PHP.

Found something (a dead project which doesn’t work anymore that enables class overloading): http://pecl.php.net/package/runkit

Possibly another project (also dead of course): http://pecl.php.net/package/apd