Pass object function as callback-CodePudding

are there ways to pass a "method reference" to a function that accept a callback?

Eg.:

function ex($callback){
   $callback();
}

$obj = (object) ['f' => function(){echo "hello";}];
ex($obj->a)

Obviously this is a very simplistic case, image having a complex object $obj with parameters inside

CodePudding user response：

PHP does not work like Javascript.

This code:

$obj = (object) ['f' => function(){echo "hello";}];

Does not define "an object with method f()" it defines "an object with property f that happens to be a callable type".

Calling $obj->f(); directly results in:

Fatal error: Uncaught Error: Call to undefined method stdClass::f()

It would need to be specially handled like:

$func = $obj->f;
$func();

Or:

($obj->f)();

While not a wholly accurate statement, you could consider it that callable types need the equivalent of "being dereferenced" before they can actually be called.

You example is something of a "successful error" in that it attempts to use "first class functions" which PHP does not have, but on a malformed object that allows this to not fail.

Using a proper class:

function ex($callback){
   $callback();
}

class Example {
  public function f_instance() {
    echo "instance call\n";
  }
  
  public static function f_static() {
    echo "static call\n";
  }
}

ex(['Example', 'f_static']);

$e = new Example();
ex([$e, 'f_instance']);

Output:

static call
instance call

Ref: https://www.php.net/manual/en/language.types.callable.php