How do I use a class method as a callback function?

Question

If I use array_walk inside a class function to call another function of the same class

class user
{
   public function getUserFields($userIdsArr         


        

Answer 1

To call a class method as a callback function in another class method, you should do :

public function compareFucntion() {
}

public function useCompareFunction() {
  usort($arrayToSort, [$this, 'compareFucntion'])
}

Answer 2

If you want to specify a class method as a callback, you need to specify the object it belongs to:

array_walk($fieldsArray, array($this, 'test_print'));

From the manual:

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

Answer 3

If you need to call a static method without instantiating the class you could do so:

// since PHP 5.3
array_walk($fieldsArray, 'self::test_print');

Or from outside:

// since PHP 5.5
array_walk($fieldsArray, User::class.'::test_print');