How to use arrow functions in PHP?

Question

I got to know about arrow functions in PHP 7.4. I tried using them like

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Answer 1

The arrow functions can make your code shorter and more readable in some situations. They were primarily designed with a thought of using them for simple callbacks. As an example consider usort() which takes in a callback function as a user parameter.

Prior to PHP 7 you had to do something like this to define your own callback for usort():

// old syntax prior to PHP 7
function cmp($a, $b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

$a = [3, 2, 5, 6, 1];

usort($a, "cmp");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}

PHP 7 has added a spaceship operator and now thanks to arrow functions you can make your code much cleaner.

// New syntax since PHP 7.4
$a = [3, 2, 5, 6, 1];

usort($a, fn($a, $b) => $a<=>$b);

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}

Try it online at 3v4l.org

Anonymous functions in PHP can be quite verbose, even when they only perform a simple operation, hence the reason for a shorter syntax. As another example consider the following function:

// Returns an array with each element squared - old syntax
function array_square($arr) {
    return array_map(function($x) { return $x*$x; }, $arr);
}

// Returns an array with each element squared - new syntax
function array_square($arr) {
    return array_map(fn($x) => $x**2, $arr);
}

print_r(array_square([1,2,3,4,5]));

Reducing the unnecessary syntax helps to understand the real purpose of the code, but keep in mind that shorter does not always mean cleaner! I would recommended to treat arrow functions with the same caution as ternary operators. Only use them when you know it helps readability, not just to make your code shorter.