Jonathan at DivisionByZero wrote up a nice article about some sites & strategies PHP devs should know about. Especially those new to PHP development.
I especially agree with the PHP Manual. PHP is highly community-driven, and the manual shows that. Almost any function you search for in the manual, you’ll see a ton of community comments relating uses, caveats, etc. I’ve been working with PHP for many years and I still hit the manual probably twice per week.