How to run psr.exe from php script in Testlink?

Question

I want to integrate psr.exe in a plugin that will be used in Testlink. the problem that i am facing is how to open the psr tool from my php code into Testlink. i found how to start the psr from Command line in this link. simply i used this command and it worked perfectly in Powershell:

psr.exe /start /output C:\test2.zip /sc 1 /gui 1 /stopevent 1233

i have developped a simple page application (not in Testlink) to try if this will work from a php code and it worked fine. however when i tried the same code into the Testlink-plugin, it didn't worked as expected.

try {
 if (isset($_POST['btn_1'])) {

     $cmd = 'psr.exe /start /output C:\test.zip /sc 1 /gui 1 /stopevent 123';     
     pclose(popen('start /B cmd /C "'.$cmd.' >NUL 2>NUL"', 'r')); 
     echo"Test started...";
     }

 elseif (isset($_POST['btn_2'])) {

     exec('psr.exe /stop');
     echo "test finish";
     }
}

 catch(Exception $e) {
 echo 'Message: ' .$e->getMessage();
 } 

above is the code that i have tried to execute the command from php, as you can see i tried to use popular used fonction in php that run an external program.

i hope that someone can guide me on this, and thanks in advance.