PHP Call closure under stdClass

Question

This is what I have

$x = new \stdClass();
$x->cast = function($y){
    return $y;
};

and when I try to execute it

$x->cast(5);

I get this error

Fatal error: Call to undefined method stdClass::cast()

How can I fix it?

Answer 1

The problem is that you're defining a variable and assigning it a closure function inside your stdClass

If you want to understand why calling $x->cast(5); doesn't work it's because PHP is looking for a method of the class named 'cast' but there is no such method instead only a property named 'cast', properties and methods are two different things for PHP

So for what you want to achieve to work you need to call (PHP 7+ syntax only)

($x->cast)(5);

Or for PHP 5.3+

$x->cast->__invoke(5)

Or for any version

call_user_func($x->cast, 5);

to tell the compiler that first you want to access the variable (which returns the closure) and then to call this closure with the parameter 5

Answer 2

In general it's nicer to just make a class if you want to attach functions to objects but in case you really want this then this should work:

$x = new \stdClass();
$x->cast = function($y){
    return $y;
};

$y = $x->cast;

var_dump($y(5));

or

call_user_func($x->cast, 5);