PHP Closure On Class Instance

Question

If I have a class like:

class MyClass
{
   public function foo() 
   {
      echo "foo";
   }
}

And then outside of the class instantiate it and try to create an anonymous function in it:

$mine = new MyClass();

$mine->bar = function() {
   echo "bar";
}

And then try to call it like $mine->bar(), I get:

Fatal error: Call to undefined method MyClass::bar() in ...

How can I create an anonymous function / closure on a class instance?

Aside: Before you tell me I should rethink my logic or use interfaces and OOP properly, in my case, it's a convenience method that applies to this specific instance of a bastardized class in an attempt to clean-up a legacy procedural application. And yes, I'm using PHP 5.3+

Daniel W. · Accepted Answer · 2013-12-13 22:38:31Z

3

See my blog article here: http://blog.flowl.info/2013/php-container-class-anonymous-function-lambda-support/

You need to add a magic __call function:

public function __call($func, $args) {
    return call_user_func($this->$func, $args);
}

The problem is that within this construct you can call private methods from public scope. I suggest not to simply add new variables to a class that are not defined. You can avoid this using magic __set functions and catch all undefined variables in a container (= array, like in my blog post) and change the call_user_func behaviour to call only inside the array:

// inside class:
public $members = array();

public function __call($func, $args) {
    // note the difference of calling only inside members:
    return call_user_func($this->members[$func], $args);
}

answered Dec 13, 2013 at 22:38

Daniel W.

32.6k15 gold badges99 silver badges155 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jeremy Harris Over a year ago

Great! It just so happened the class extended a class implementing magic methods so it was no sweat adding this in. One addition I made is to check with is_callable() before actually calling it. Thanks!

Daniel W. Over a year ago

this can be extended in some ways, but you get the idea behind it B-)

M K · Accepted Answer · 2013-12-13 22:43:42Z

1

__call

This will work.

class Foo {

    public $bar;
    public function __construct()
    {
        $this->bar = function()
        {
            echo 'closure called';
        };

        $this->bar();
    }

    public function __call($method, $args) {
        return call_user_func($this->$method, $args);
    }

}

new Foo();

answered Dec 13, 2013 at 22:43

M K

9,4567 gold badges46 silver badges45 bronze badges

1 Comment

M K Over a year ago

First come - first served :)

Te Ko · Accepted Answer · 2013-12-13 22:45:32Z

1

The function IS being created. PHP has a problem with calling it.

Dirty, but works:

$f = $mine->bar;
$f();

answered Dec 13, 2013 at 22:45

Te Ko

7683 silver badges13 bronze badges

2 Comments

Jeremy Harris Over a year ago

Interesting. Reminds me of the issue with dynamic namespaces. You have to put it in a variable first before instantiating like $ns = "\\App\\Lib\\" . $myClass; $object = new $ns();`

Daniel W. Over a year ago

@cillosis you can (at least in PHP 5.4) use brackets: $object = new {$ns}(); same with fluent classes: does not work: $x = new xxx()->method(); does work: $x = (new xxx())->method();

Collectives™ on Stack Overflow

PHP Closure On Class Instance

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related