Web resources

The best place to start is to check the list of links at the official PHP site, http://www.php.net/links.php.

Here are some resources we frequently use:

http://www.php.net/manual/: The annotated online PHP manual at the official PHP site. Includes many comments for each library and function and tips on use and common problems encountered.
http://www.zend.com: Site of the commercial company held by long-term developers of PHP. Includes articles, resources, free code, and tutorials.