PHP program to create a new function that composes multiple functions into a single callable.

<?php
//Licence: https://bit.ly/2CFA5XY
function compose(...$functions)
{
    return array_reduce(
        $functions,
        function ($carry, $function) {
            return function ($x) use ($carry, $function) {
                return $function($carry($x));
            };
        },
        function ($x) {
            return $x;
        }
    );
}
$compose = compose(
    // add 2
    function ($x) {
        return $x + 2;
    },
    // multiply 4
    function ($x) {
        return $x * 4;
    }
);
print_r($compose(2));
echo("\n");
print_r($compose(3));

?>

Output:

16
20