Although I am certain that having a PHP certification is not the only way to demonstrate that a PHP developer is really qualified, I am sure that it helps hinting employers about his skills, and so become more open to negotiate better salaries. Having a PHP certification also helps a developer stand out from the crowd of developers that apply to a job but do not have any certification.

In the interview Manuel talks with Mauricio (a Brazilian PHP developer) about whether or not he feels the certification is worth it, how a developer can take it and what they need to do to prepare for it as well as a mention of a book that might help.

Michael Kimsal has also posted some of his own thoughts on the certification issue (and of the comments made during the interview).

Every so often I try to use PDO under PHP5, and every time I run in to basic functionality problems with no ability to find out what's going on under the hood.

He includes a few comments supporting his statement including an issue where a prepare() call didn't work, his frustration with not being able to see what's "under the hood" and the lack of documentation to help with these sorts of issues.