Even though I'm a pretty hardcore PHP programmer I rarely "socialize" with other programmers. The times I do, I usually learn some good tricks. So, share some tools, classes and scripts that you use frequently.
Here are mine:
1. ADODB (
http://adodb.sourceforge.net) - database abstraction lawyer with result cashing and a bunch of other good things.
2. Smarty (
http://smarty.php.net) - template engine with built-in page caching.
3. Snoopy (
http://snoopy.sourceforge.net) - web client class. Useful for fetching other pages.
4. JP Cache (
http://www.jpcache.com) - full page caching class
5. NuSOAP (
http://dietrich.ganx4.com/nusoap/index.php) - SOAP engine for data exchange and RPC calls