Simply put, the differences between 4.3.x and 5.0.0 versions of tidy (tidy versions 1.0 and 2.0) are significant In Tidy for 1.0, you could only manipulate one document at once. Although Tidy 1.0 worked in PHP 5 (allowing for some of the parsing abilities you've seen), the API has since been refactored to be easier to use ]]>