PHP Arrow Functions

With version 7.4 PHP introduced arrow functions, which are anonymous functions with a shorter syntax. Anonymous functions mostly come in handy for callback functions, when filtering an array for example:

<?php

$numbers = [-4, 1, 8, 0];
$positive = array_filter($numbers, fn($n) => $n >= 1);
//=> [1, 8]

Arrow functions are defined using the fn keyword and can only have one expression, for which the result is used as the return value. Therefore there is no need for the return statement, it's not even allowed actually.

Arrow functions differ from anonymous functions in that they don't require the use keyword in order to use variables from outside the function scope.