If you want to validate IPs using this function, please be careful:
The function filter_var should be used instead for validating IPs.
<?php
$ip = '192.168.0355.24';
var_dump(ip2long($ip) !== false); // true (expected false)
var_dump(filter_var($ip, FILTER_VALIDATE_IP) !== false); // false
$ip = '192.168.355.24';
var_dump(ip2long($ip) !== false); // false
var_dump(filter_var($ip, FILTER_VALIDATE_IP) !== false); // false
?>