PHP: How to use a class function as a callback [du

Question

This question already has an answer here:

• How do I dynamically invoke a class method in PHP? 8 answers

I have a class with methods which I want to use as callbacks. How to pass them as arguments?

Class MyClass {

    public function myMethod() {
        $this->processSomething(this->myCallback); // How it must be called ?
        $this->processSomething(self::myStaticCallback); // How it must be called ?
    }

    private function processSomething(callable $callback) {
        // process something...
        $callback();
    }

    private function myCallback() {
        // do something...
    }

    private static function myStaticCallback() {
        // do something...
    }   

}

UPD: How to do the same but from static method (when $this is not available)

Answer 1

Check the callable manual to see all the different ways to pass a function as a callback. I copied that manual here and added some examples of each approach based on your scenario.

Callable

---

• A PHP function is passed by its name as a string. Any built-in or user-defined function can be used, except language constructs such as: array(), echo, empty(), eval(), exit(), isset(), list(), print or unset().

  // Not applicable in your scenario
  $this->processSomething('some_global_php_function');

---

• A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1.

  // Only from inside the same class
  $this->processSomething([$this, 'myCallback']);
  $this->processSomething([$this, 'myStaticCallback']);
  // From either inside or outside the same class
  $myObject->processSomething([new MyClass(), 'myCallback']);
  $myObject->processSomething([new MyClass(), 'myStaticCallback']);

---

• Static class methods can also be passed without instantiating an object of that class by passing the class name instead of an object at index 0.

  // Only from inside the same class
  $this->processSomething([__CLASS__, 'myStaticCallback']);
  // From either inside or outside the same class
  $myObject->processSomething(['\Namespace\MyClass', 'myStaticCallback']);
  $myObject->processSomething(['\Namespace\MyClass::myStaticCallback']); // PHP 5.2.3+
  $myObject->processSomething([MyClass::class, 'myStaticCallback']); // PHP 5.5.0+

---

• Apart from common user-defined function, anonymous functions can also be passed to a callback parameter.

  // Not applicable in your scenario unless you modify the structure
  $this->processSomething(function() {
      // process something directly here...
  });

---

Answer 2

Since 5.3 there is a more elegant way you can write it, I'm still trying to find out if it can be reduced more

$this->processSomething(function() {
    $this->myCallback();
});

Answer 3

You can also to use call_user_func() to specify a callback:

public function myMethod() {

    call_user_func(array($this, 'myCallback'));
}

private function myCallback() {
    // do something...
}