I unable to read data from weighment machine , for some machine its fine but for some machine its not working

I tried to read serial port data(which is connected to weighment machine) using php dio exntension(https://pecl.php.net/package/dio). For some weighment machines it's working fine but on some  machines it's not reading the data. I have shown my function below which reads the data from the serial port. Can somebody give me the solution :

//Function which read the data from serial port
    public static function getWeight($portName = '', $baudRate = '', $dataBit = '', $stopBit = '')
    {
        $bbSerialPort;
        $bbSerialPort = dio_open($portName, O_RDWR); //open port with read and write permission
        //we're on windows configure com port from command line
        shell_exec("mode {$portName} baud={$baudRate} data={$dataBit} stop={$stopBit} parity=n xon=on");
        $runForSeconds = new DateInterval("PT1S");
        $endTime = (new DateTime())->add($runForSeconds);
        $abc = '';
        //loop for 1 seconds
        while (new DateTime() < $endTime) {
            $data = dio_read($bbSerialPort, 512); //this is a blocking call
            if ($data) {
                preg_match('/(:\d+)/', $data, $abc);
                if (count($abc)) {
                    $abc = $abc[0];
                    if ($abc) break;
                }
            }
        }
        dio_close($bbSerialPort);
        return $abc;
    }