This is a very simple PHP Whitelist Library.
The Whitelist separates items read from a file by newlines.
There aren't many uses for a Whitelist in PHP, but I use it to limit which links I allow to be converted to BackLinks. But you could use it to limit other things. Recently I decide to throw it in the Public Domain for everyone. A Whitelist solution in PHP was non-existent when I needed one , so I decided to make one.