How to run roscore from php using shell script?

edit

Hi, Need help to figure out how to execute roscore or launch files from the web.

To do this, I created startup.php that calls a startup.sh file from the web. This shell script calls the roscore command. The echo is printed out however, the roscore command does not run.

startup.php

<?php
if ($_GET['run']) {
  # This code will run if ?run=true is set.
  $output = shell_exec("sh /var/www/html/startup.sh");
  echo "<pre>$output</pre>";
}
?>
  # This code will run if ?run=true is set.
  $output = shell_exec("sh /var/www/html/ros_startup.sh");
  echo "<pre>$output</pre>";
}
?>
<!-- This link will add ?run=true to your URL, myfilename.php?run=true -->
<a href="?run=true">Click Me!</a>

startup.sh

#!/bin/bash
clear
echo "Start..." 
source /opt/ros/kinetic/setup.bash
roscore
echo "Completed..."