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<?php $re = '/^(?\'a\'1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.(?&a)$/m'; $str = '255.255'; preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0); // Print the entire match result var_dump($matches);

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