The sheer number of PHP resources is overwhelming. Here are some of the more important parts of PHP that are often overlooked:
PHP's Official Web Site (http://php.net/)
Everyone knows and visits the PHP web site. However, there is a lot of information on the site. It is often worth the time digging around on php.net before going anywhere else. Some of the information on the site is a bit hard to find, but is well worth the effort.
PHP Conference Presentation Archive (http://conf.php.net/)
A good number of the presentations given by leading PHP community members is archived on this site.
PHP4WIN (http://www.php4win.com/)
PHP4Win is an excellent resource center for developers who run PHP on Windows.
The PHP Mailing List Archives (http://php.net/support.php)
The PHP mailing list archives contain a wealth of information. Many of the mailing lists have been continuously archived for several years. Stored in the archives are the answers to many questions.
Snapshots of Recent Development Builds of PHP (http://snaps.php.net/)
PHP has a very rapid development cycle. Features are added and bugs are fixed on a daily basis. If you want to get the latest version of PHP to take advantage of a new feature or a bug fix, you can visit this site to download a version of PHP that is a few hours or days old.
Web-based Browsers for the PHP Source
There are three different online tools that allow you to browse through the CVS repository. CVS is a version control software tool that the developers of PHP use to manage the many hundreds of files that make up the PHP project. For more information on CVS, visit http://www.cvshome.org/.
These browsers can be found at:
http://cvs.php.net/ provides a straightforward interface to PHP's CVS repository
http://bonsai.php.net/
http://lxr.php.net/ provides powerful searching and indexing features above and beyond what is provided by http://cvs.php.net/
PHPBuilder (http://www.phpbuilder.com/)
PHPBuilder is a comprehensive web site where people post information about combining PHP with just about everything. There is plenty of support and documentation available on this web site.
The Apache Project (http://www.apache.org/)
The official web site for the most popular web server on the planet. This site contains documentation on installing, configuring, and troubleshooting the Apache web server, as well as useful information about making your own modules for the server.
The Official MySQL Site (http://www.mysql.com/)
MySQL is the database of choice for many PHP programmers. It is released under the MySQL Free Public License. For more information on the license please refer to the official MySQL site.
The Official PostgreSQL Site (http://www.postgreSQL.org/)
This is where you can find more on the history of PostgreSQL, download copies of PostgreSQL, browse the official documentation, and much more besides, including how to pronounce PostgreSQL.