Zend Technologies have recently launched their Certification program for the PHP scripting language:
As the PHP company, Zend has been approached by many asking it to establish an industry standard that recognizes PHP expertise. The PHP certification exam encompasses curriculum criteria specified by the Zend PHP Education Advisory Board as essential to demonstrate expert proficiency in PHP.
I'm a member of the above mentioned advisory board and helped developing the questions (and answers, of course) for the certification. Working on the exam has been both challenging and enjoyable: Challenging because figuring out good questions can be extremely hard, enjoyable because working on interesting stuff with interesting folks is so ... enjoyable.
The exam covers the full range of PHP tasks in web development and it is really, really well made. If you are looking for a solid confirmation for your (or for your employees', if you are in the entrepreneur business) PHP skills, then join the program; you won't be disappointed.
And yes, I get wages for every participant. Thanks for not asking.