f=1 means save thumbnail on the server. Nothing to show in the browser. f=0 - show in the browser and do not save on server.
Do you need both big image and thumbnail? I'm not sure i understand what you are trying to achieve. What is "cat" parameter?
http://www.something.com/admin/thumb.php?cat=news&src=news1.jpg&dest=news1-thumb.jpg&f=1&x=71&y=51
As i understand you want above URL to create thumbnail from the image. Correct?
You have both thumbnail folder and images folder set to the same folder in the script (
/home/something.com/public_html/images/'.$_GET['subfolder'].'/'). Correct?
If so, script will take
news1.jpg from the
/home/something.com/public_html/images/'.$_GET['subfolder'].'/', make thumbnail, and save it in the same folder. Nothing will be shown in the browser as f=1 means save file on the server.