Something like a callback delegate function in php

Question

I would like to implement something similar to a c# delegate method in PHP. A quick word to explain what I\'m trying to do overall: I am trying to implement some asynchron

Answer 1

How do you feel about using the Observer pattern? If not, you can implement a true callback this way:

// This function uses a callback function. 
function doIt($callback) 
{ 
    $data = "this is my data";
    $callback($data); 
} 


// This is a sample callback function for doIt(). 
function myCallback($data) 
{ 
    print 'Data is: ' .  $data .  "\n"; 
} 


// Call doIt() and pass our sample callback function's name. 
doIt('myCallback'); 

Displays: Data is: this is my data

Answer 2

(Apart from the observer pattern) you can also use call_user_func() or call_user_func_array().

If you pass an array(obj, methodname) as first parameter it will invoked as $obj->methodname().

<?php
class Foo {
    public function bar($x) {
        echo $x;
    }
}

function xyz($cb) {
    $value = rand(1,100);
    call_user_func($cb, $value);
}

$foo = new Foo;
xyz( array($foo, 'bar') );
?>

Answer 3

I was wondering if we could use __invoke magic method to create "kind of" first class function and thus implement a callback

Sound something like that, for PHP 5.3

interface Callback 
{
    public function __invoke(); 
}

class MyCallback implements Callback
{
    private function sayHello () { echo "Hello"; }
    public function __invoke ()  { $this->sayHello(); } 
}

class MySecondCallback implements Callback
{
    private function sayThere () { echo "World"; }
    public function __invoke ()  { $this->sayThere(); }
}

class WhatToPrint
{
    protected $callbacks = array();
    public function register (Callback $callback) 
    {
        $this->callbacks[] = $callback;
        return $this;
    }
    public function saySomething ()
    {
        foreach ($this->callbacks as $callback) $callback(); 
    }
}

$first_callback = new MyCallback;
$second_callback = new MySecondCallback;
$wrapper = new WhatToPrint;
$wrapper->register($first_callback)->register($second_callback)->saySomething();

---

Will print HelloWorld

Hope it'll help ;)

But I'd prefer the Controller pattern with SPL for such a feature.