PHP has a number of places you can look to see if what you need is already made. That can save you time and effort--even with you hacking on it to customize it to your needs. Database abstraction classes, PHP extensions, templates, content management systems and frameworks are just some of the wheels already created. Why reinvent the wheel when you don't have to?
PEAR and PECL
PEAR (PHP Extension and Application Repository) and PECL (PHP Extension Community Library) are PHP sanctioned repositories. PEAR is for PHP classes you include in your scripts to get added functionality. A few commonly used PEAR classes are PEAR::DB and PEAR::MailMime. PECL is for PHP extensions written in C that you build into your PHP interpreter to give you "more functions" to use in your code. PECL extensions sometimes make it into the PHP core libraries. A few commonly used PECL extensions are APC (Alternative PHP Cache) and pdflib.
sourceforge or freshmeat
Sourceforge.net and freshmeat.net are two repositories for open source projects. Each has thousands of projects available covering numerous categories in various states of maturity. What you want/need may already be available. The two large and commonly used projects phpMyAdmin and Gallery are available through sourceforge and freshmeat.
Google is your friend
And when in doubt, Google is your friend. Many projects and scripts have their own sites or are available through the many PHP developer sites and can only found if you search for them through a search engine. Tutorials, code snippets, people's personal classes, frameworks-- to name a few things-- are best found through your preferred search engine.
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