Hi, waerfwe -
1. Edit the PHP source file (EX: /var/www/myfile.php) with gedit
2. Make your changes and SAVE with gedit
3. VIEW with your web browser (EX: firefox, http://localhost/myfile.php
Reason for step 3) being separate from steps 1) and 2):
The apache server needs to INTERPRET your PHP file (in order for you to see what you expect to see). Using a browser is the most practical way to request the server to process the file. Dragging and dropping the file to Firefox, on the other hand, completely bypasses the server.