HTML5DOMDocument is a PHP library for parsing and manipulating HTML5 code. It has almost 500 stars on GitHub and a nice set of features. But the thing that I like the most is its performance. I've spent a lot of time optimizing each operation. It's heavily used in all Bear CMS and Alle.bg websites, so each shaved millisecond makes a huge difference at the end of the day.

Check it out at GitHub. And this is the announcement post.