public static function oath_hotp($key, $counter){ $bin_counter = pack('n*', 0) . pack('n*', $counter); // counter must be 64-bit int $hash = hash_hmac ('sha1', $bin_counter, $key, true); return str_pad(self::oath_truncate($hash), self::otplength, '0', str_pad_left);}public static function oath_truncate($hash){ $offset = ord($hash[19]) & 0xf; return ( ((ord($hash[$offset+0]) & 0x7f)
self::otplength是类中的一个变量