从PHP运行屏幕并使用东西

I am new to PHP and need to run a screen session & send a character using stuff. My code is as below -

Call from the PHP code

if (!empty($key))
{
    system("/bin/bash test.sh " . $key);
}

I create a screen called as arduino by below

/usr/bin screen -dmS arduino /dev/ttyUSB0 9600

Call from the script file from test.sh

/usr/bin screen -S arduino -X stuff "$1"$'
'

Is the format using 'stuff' command right - i want to send a character like x,w,d followed by 'enter'.

I have added my user to www-data already. I have checked PHP.ini but nothing out of ordinary. My web server is Apache2 and runs on /var/www

Any suggestions please?