modify a method/function at runtime

Question

I've been looking at the php reflection methods, what i want to do is inject some code after the method is opened and before any return value, for example i want to change:

function foo($bar)
{
    $foo = $bar ;
    return $foo ;
}

And inject some code into it like:

function foo($bar)
{
    //some code here
    $foo = $bar ;
    //some code here
    return $foo ;
}

possible?

Answer 1

Well, one way, would be to make all the method calls "virtual":

class Foo {
    protected $overrides = array();

    public function __call($func, $args) {
        $func = strtolower($func);
        if (isset($this->overrides[$func])) {
            // We have a override for this method, call it instead!
            array_unshift($args, $this); //Add the object to the argument list as the first
            return call_user_func_array($this->overrides[$func], $args);
        } elseif (is_callable(array($this, '_' . $func))) {
            // Call an "internal" version
            return call_user_func_array(array($this, '_' . $func), $args);
        } else {
            throw new BadMethodCallException('Method '.$func.' Does Not Exist');
        }
    }

    public function addOverride($name, $callback) { 
        $this->overrides[strtolower($name)] = $callback;
    }

    public function _doSomething($foo) {
        echo "Foo: ". $foo;
    }
}

$foo = new Foo();

$foo->doSomething('test'); // Foo: test

PHP 5.2:

$f = create_function('$obj, $str', 'echo "Bar: " . $obj->_doSomething($str) . " Baz";');

PHP 5.3:

$f = function($obj, $str) {
    echo "Bar: " . $obj->_doSomething($str) . " Baz";
}

All PHP:

$foo->addOverride('doSomething', $f);

$foo->doSomething('test'); // Bar: Foo: test Baz

It passes the instance of the object as the first method to the "override". Note: This "overriden" method will not have access to any protected members of the class. So use getters (__get, __set). It WILL have access to protected methods, since the actual call is coming from __call()...

Note: You'll need to modify all your default methods to be prefixed with an '_' for this to work... (or you can chose another prefix option, or you can just scope them all protected)...

Answer 2

Look into anonymous functions. If you can run PHP 5.3 that might be more along the lines of what you're trying to do.