Thanks LordShryku. On Linux, I was able to do it this way:
if(exec("/usr/local/bin/php cmdlineprocess.php &")) {
echo "Executed";
}
else {
echo "Can't Execute";
}
However, I was hoping that by doing it this way php would execute the script as a separate process and free up the web script to continue. The cmdlineprocess.php script can take up to 5 minutes to run. Has anybody done this on Linux.