// Sorry, currently I did not make a routine for IPv6, // but I'm sure you find one at: http://regexlib.com/ function IsIPValid($ip){ if (preg_match('/^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/', $ip)){ return true; } return false; } // examples: var_dump(IsIPValid('192.168.100.1')); // => bool(true) var_dump(IsIPValid('192...1')); // => bool(false) var_dump(IsIPValid('127001')); // => bool(false) var_dump(IsIPValid('127.0.0.1')); // => bool(true)