Anonymous functions, also known as closures, allow the creation of functions which have no specified name.
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:
