Why and how do you use anonymous functions in PHP?

Question

Anonymous functions are available from PHP 5.3.
Should I use them or avoid them? If so, how?

Edited; just found some nice trick with php anonymous functions...

$container           = new DependencyInjectionContainer(); $container->mail     = function($container) {}; $conteiner->db       = function($container) {}; $container->memcache = function($container) {}; 

Answer 1

Anonymous functions are useful when using functions that require a callback function like array_filter or array_map do:

$arr = range(0, 10); $arr_even = array_filter($arr, function($val) { return $val % 2 == 0; }); $arr_square = array_map(function($val) { return $val * $val; }, $arr); 

Otherwise you would need to define a function that you possibly only use once:

function isEven($val) { return $val % 2 == 0; } $arr_even = array_filter($arr, 'isEven'); function square($val) { return $val * $val; } $arr_square = array_map('square', $arr);