Luhn algorithm implementation for validate credit card number

cardNumberValidate.php

<?php

/*
-(bool) luhnValidate ("number");
*/

function luhnValidate($string) {
	$string = preg_replace("![^0-9]!","",$string);
	$result = "";
	foreach (str_split(strrev((string) $string)) as $i => $d) { $result .= $i %2 !== 0 ? $d * 2 : $d; }
	return array_sum(str_split($result)) % 10 === 0;
}