No, the process will not pickup where it has left. It will start over again unless you specificly tell it to start where it stopt.
I.e. this php scruot does the utterly pointless task of adding one to a number:
$i = $_GET['i'];
while(true)
print $i++;
If you write down the last number when stopping the server and then restart the script with the correct $_GET['i'] it will start where it has left of, but only because you made it do so. The script state is not saved when restarting.
EDIT
You could also have it safe the current state to the filesystem or database so you won;t have to enter it by hand.
EDIT 2
Ohh, so you wan't to stop the progress. If restarting XAMP didn't stop it then you will have to give more info on what is happeing since restarting XAMP should stop the execution of all PHP scripts.