$re = '/^(((25[0-5])|(2[0-4]\d)|(1\d{2})|(\d{1,2}))\.){3}(((25[0-5])|(2[0-4]\d)|(1\d{2})|(\d{1,2})))$/m';
$str = '1.1.1.1
254.2.2.2.
255.1.1.255
256.1.1.256
012.111.111.111
12.12.12.12a
1q.1.1.1
1.1q.1.1
1.1.1q.1
1.1.1.1q
abcde254.2.2.2';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php