PHP CALLBACK FUNCTIONS

PHP CALLBACK FUNCTIONS

• A callback function (often referred to as just "callback") is a function which is passed as an argument into another function.
• Any existing function can be used as a callback function. 
• To use a function as a callback function, pass a string containing the name of the function as the argument of another function.
• A callback is a function passed as an argument to another function.
•  This technique allows a function to call another function.
• A callback function can run after another function has finished.

TYPES OF CALLBACK FUNCTIONS IN PHP :

• Simple callback.
• Static class method call
• Object method callback.
• Callback using a Closure.

RETURNING A CALLBACK IN PHP :

• In returning a callback, the called function returns a callback instead of executing it immediately.
• The calling code where the callback is returned can execute the returned callback immediately, pass it to some other function and so on.

EXAMPLE FOR CALLBACK FUNCTIONS IN PHP :

<?php
//Function to callback
 function my_callback_function()

 {
      echo 'Hello, Rosa!';
}
//PASS my_callback_function INTO call_user_func()
call_user_func('my_callback_function');
?>

 Output :

Hello, Rosa!