Have you ever wonder about that how you can temporary (or may be permanent, too) disable the GD Library support for PHP in you Linux box? Well, here is a trick reference for you.
I use Ubuntu 12.04 in my development machine and use LAMP as a local web server for development purpose. Recently I was working in a project where GD library is a essential dependency and I had to check the behavior of the code I wrote under a server environment where GD library is not available. You may want to find the way that I did tweak and checked.
Find the file: /etc/php5/apache2/conf.d/gd.ini and open it with root privilege in gedit (or any other text editor)
sudo gedit /etc/php5/apache2/conf.d/gd.ini
Put a semicolon in front of the line says, extension=gd.so make it looks like:
; configuration for php GD module
Then save and close the file.
Now reload the apache2 configuration
sudo service apache2 reload
And now you have GD Library is installed but disabled in your system.
“The Reverse Sweep”
To enable it back, just follow the entire process except uncommenting the 2nd line in step two instead of commenting with a semicolon.