For interest, wondering what PHP libraries people use? By use I mean libraries you actually trust and are willing to use / have used on a live website.
To get the ball rolling, some I’ve used before;
Email: phpMailer – 100% happy. Also a great place to help beginners understand the basic purpose of OOP
DB: ADOdb when working with Oracle – the API is much friendlier than the native Oracle extensions
XML-RPC: Incutio XML-RPC Library – the “off the shelf” version has one or two bugs which show up in less common situations but this is one of the most complete and easy-to-use XML-RPC implementations in PHP available, IMO. What I like most is it takes full advantage of PHP’s dynamic nature, rather than needing a ton of glue code to map types.
HTTP client: PEAR::HTTP_Request – there’s one of two things I’d like to fix but in general it’s a workhorse I can live with.
Forms: PEAR::HTML_QuickForm for one-off, standalone scripts. WACT otherwise.
RSS Generation: Manuel Lemos’s RSS Writer
Caching: PEAR::Cache_Lite – when I’m in a hurry. Running it through a profiler though makes me consider writing my own, specific / tuned to a particular problem.