Lauching program via command in php

Question

i have tried to launch Firefox using the php exec() and system() function but it only launches up as a process in the task-manager without showing the browser window.What could be the problem?I have event tried using a bat and executing it to launch Firefox but its not working.I have tried many solutions from questions in this forum but non is working.Below is my code

    <?php
       exec('c:\WINDOWS\system32\cmd.exe /c START firefox.exe');

       system("cmd /c C:\my\project\folder\launcher.bat");

     ?>