CODEWITHSUNDEEP
phpclassinstanceanonymous-function
geekay
geekay

Reputation: 107

php Set a anonymous function in an instance

I am just starting out with PHP, and I am wondering if there is a way to add an anonymous function to a class instance.

For instance, lets say...

class A{
    public B;
}

$c = new A();

//This is where I am getting a little confused...
//The following wont work

$c->B = function(){echo('HelloWorld');};
$c->B();

What I am hoping to do is reuse the same spit of code in a great number of different applications, and make it so that I can just 'swap-out' and replace functions in specific instances.

I am using php5.3 (so anonymous functions should work, just not in the way that I am using them).

Thanks so very much for your time!!

-GK

Upvotes: 7

Views: 3690

Answers (7)

Kerem
Kerem

Reputation: 11576

This is not an issue anymore by PHP 7;

// no error
$result = ($this->anonFunc)();
$result = ($this->anonFunc)($arg1, $arg2, ...);

See more about AST.

Upvotes: 1

Lee Davis
Lee Davis

Reputation: 4756

Rather than hooking a __call magic method into your class, you can instead execute the callable directly using call_user_func. 

class A {
    public $b;
}

$c = new A();
$c->b = function(){echo('HelloWorld');};

call_user_func($c->b);    // HelloWorld

Obviously it would be nice for PHP to provide some syntax to execute this directly.

Upvotes: 0

therufa
therufa

Reputation: 2041

You can use the __call magic function for this job. Not a beauty, but it works..

like this: 

class A {
    public $B;

    public function __call($closure, $args)
    {
        call_user_func_array($this->$closure, $args);
    }
}

$c = new A();

$c->B = function () { echo('HelloWorld'); };
$c->B();

Upvotes: 10

Charles
Charles

Reputation: 51411

FWIW:

PHP 5.3's treatment of anonymous functions is entertaining. This won't work:

$c->B = function() { echo func_get_arg(0); };
$c->B("This fails :(");

This WILL work:

$c->B = function() { echo func_get_arg(0); };
$hilarious = $c->B;
$hilarious("This works!");

To work around this, you need to use a __call hack like the one provided by Oden.

This behavior may change in the future. The array dereferencing RFC was recently committed to PHP's trunk, and the patch has set off a discussion on function call chaining, the syntax of which may allow what you're trying to do without the __call hack. Unfortunately it's proven difficult in the past to get function call chaining working.

Upvotes: 5

user358390
user358390

Reputation: 637

# real ugly, but PoC...

class a {
  function __call($f, $x) {
    call_user_func_array($this->$f, $x);
  }
}

$a = new a;
$a->b = function() { echo "Hello world"; };
$a->b();

Upvotes: 4

Paul Dixon
Paul Dixon

Reputation: 300845

Sounds like you are describing a Strategy Pattern or Decorator Pattern - there are other ways to achieve this in way which is more easily communicated with other developers who read your code.

Upvotes: 2

Artefacto
Artefacto

Reputation: 97825

You can do something along these lines (which will also work with callbacks that are not closures):

<?php
class A {
    private $fun;
    function setFun($fun) {
        if (!is_callable($fun))
            throw new InvalidArgumentException();
         $this->fun = $fun;
    }
    public function fun() {
        call_user_func_array($this->fun, func_get_args());
    }
}

$c = new A();

$c->setFun(function($a) { echo('HelloWorld ' . $a);});
$c->fun("here");

which gives HelloWorld here.

That said, you should also consider inheritance or the decorator pattern.

Upvotes: 1

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