I wanted to throw a shout-out for PHP Whois. I used them recently for a dashboard widget in a project. This is an extremely handy PHP library. You can check them out on SourceForge at: http://sourceforge.net/projects/phpwhois/
In particular I like how it returns an array of the data, and it is quick and easy to pull out the portions you may need. Additionally it includes a really good example, along with a nice HTML format, straight text output, or a view of the PHP array.