PHP Callback Functions

PHP Callback Functions Tutorial

In PHP Callback Functions is a function that is passed as an argument to another function and is executed at a later time. Callbacks are useful for customizing behavior, array operations, or event handling.

Basic Callback Function

<?php
// Define a callback function
function myCallbackFunction($item) {
return strlen($item); // Return length of string
}

// Array of strings
$fruits = ["Apple", "Banana", "Mango"];

// Use array_map with callback
$lengths = array_map("myCallbackFunction", $fruits);

print_r($lengths);
?>

<?php

// Define a callback function

function myCallbackFunction($item) {

return strlen($item); // Return length of string

}

// Array of strings

$fruits = ["Apple", "Banana", "Mango"];

// Use array_map with callback

$lengths = array_map("myCallbackFunction", $fruits);

print_r($lengths);

Output:

array_map() applies the callback function to each element of the array.

Using Anonymous Functions as Callbacks

Output:

Anonymous functions are convenient for inline callback logic.

Callback with `usort()` (Custom Sorting)

Output:

usort() uses a callback to define custom sorting logic.

Using `call_user_func()`

call_user_func() calls a callback function dynamically:

Output:

Using `call_user_func_array()`

Allows calling a callback with an array of parameters:

Output:

Key Points About Callback Functions

A callback function can be:
- Named function
- Anonymous function
- Static class method
Useful in:
- array_map(), array_filter(), array_reduce()
- Sorting arrays (usort(), uasort())
- Event handling or dynamic function calls
call_user_func() and call_user_func_array() allow dynamic execution.

PHP Callback Functions