The application is simple. You enter a bunch of text and Wordle does the rest. The applet provides options to change color, font and layout. Just for fun I created a Wordle cloud to display php's built in functions. Two samples are shown below. The size of the font in the cloud is proportional to the number of functions starting with the particular name.
Among the largest on the list are words like "array", "get", "mysql" and "mcrypt". He used a call to the get_defined_functions() method and looped through the "internal" subarray to build his lists.