How to implement a decorator in PHP?

Question

Suppose there is a class called \"Class_A\", it has a member function called \"func\".

I want the \"func\" to do some extra w

Answer 1

None of these answers implements Decorator properly and elegantly. mrmonkington's answer comes close, but you don't need to use reflection to enact the Decorator pattern in PHP. In another thread, @Gordon shows how to use a decorator for logging SOAP activity. Here's how he does it:

class SoapClientLogger
{
    protected $soapClient;

    // this is standard. Use your constuctor to set up a reference to the decorated object.
    public function __construct(SoapClient $client)
    {
        $this->soapClient = $client;
    }

    ... overridden and / or new methods here ...

    // route all other method calls directly to soapClient
    public function __call($method, $args)
    {
        // you could also add method_exists check here
        return call_user_func_array(array($this->soapClient, $method), $args);
    }
}

And he's a slight modification where you can pass the desired functionality to the constructor:

class Decorator {

    private $o;

    public function __construct($object, $function_name, $function) {
        $this->o = $object;
        $this->$function_name = $function;
    }
    public function __call($method, $args)
    {
        if (!method_exists($this->o, $method)) {
            throw new Exception("Undefined method $method attempt in the Url class here.");
        }
        return call_user_func_array(array($this->o, $method), $args);
    }   
}