I think certification is a good idea in PHP, where programmers are a dime a dozen. PHP is such a widely used and accessible language that it’s difficult to examine potential employees without going in-depth. Contrast PHP with a language like Python; simply by virtue of knowing Python, programmers are significantly more likely to understand, adhere to, and be passionate about writing clean code using modern best-practice conventions and design patterns. Most of the PHP programmers I’ve met in my time couldn’t care less about MVC, abstraction, and proper object-oriented design. Simply stated, many PHP programmers are not computer scientists.
Certification does a number of things for you—namely, it separates you from the herd, will generally bring you higher wages, and also gives you footing to climb the ladder at the company. Comparatively, PHP programmers don’t get paid as much as those who program for other languages. Certification gives you footing to argue for a higher wage/salary and ensures that you’re taken seriously as a programmer. Also of consideration is the fact that most PHP programmers, i.e. the people you’re competing with, aren’t going to be certified. The push to make yourself recognized by industry leading bodies speaks of your professionalism and quality as a programmer.
With all that said, the only real option is Zend Certified Engineer (ZCE), the industry standard. Even if your employer doesn’t know what the ZCE is, if you put it on your resume, they can look it up on Google and quickly find that it is the most reliable way to certify you’re a skilled PHP programmer, not one who writes pathetic spaghetti code and uses boorish design patterns (if any). Certifications jump off the page when your resume is held up against the countless others which will lack definition and certifications.