Y Combinator in PHP7

ycombinator.php

<?php

function Y($le) {
    return (function ($f) {
        return $f($f);
    })(function ($f) use ($le) {
        return $le(function ($x) use ($f) {
            return $f($f)($x);
        });
    });
}

$factorial = Y(function ($fac) {
    return function ($n) use ($fac) {
        return $n <= 2 ? $n : $n * $fac($n - 1);
    };
});

echo $factorial(5);