/**
* get a part pdu string and cut them from pdu
* @param integer $length
* @return string|null
*/
public static function getPduSubstr($length)
{
$str = mb_substr(self::$_pduParse, 0, $length);
PDU::debug("PDU::getPduSubstr: " . $str);
self::$_pduParse = mb_substr(self::$_pduParse, $length);
return $str;
}
