In a recent post from Jeez.eu they look at some of the PHP certifications offered by various companies all over the web:

Becoming a certified PHP developer, does not mean that you become a better developer but, it can surely give you some more chances to get the job. We tried to do a little research about PHP certifications, where to get one, what it takes to get one and why you need it. We also tried to find some online tests for you in order to prepare yourself before you actually go for it.

There's five certifications in their list:

• the Zend certification (ZCE and ZFCE)
• a certification offered from W3 Schools
• A test from Brainbench
• ExpertRating's exam
• the O'Reilly School of Technology