I personally think certification is a after-thought business model provided by companies looking to make a buck. Practical examples: MCP (Microsoft Certified Professional) - there's too many paper MCP's out there that devalue the intended value of the MCP cert that the MCP doesn't really mean much. Plus with it expiring after a couple years, its a new revenue stream for Microsoft.
It depends on what you're goal is of the cert. When I was in a consulting firm, they required us to go out and get MCP and A+ immediately. I went and did that. All it did was allow the consulting firm to say all their consultants were MCP (MS Server v4 flavor) and A+ certified. No pay increase for me. No new job responsibilities. And it didn't help me get into web development. But the consulting firm wanted it to get more gigs.
So you could look at this PHP cert that way. To get it to land more gigs - be it consulting jobs or a full time job. But I don't think there's a lot of full time PHP jobs available out there at this moment (I may be wrong though). And if there is, I doubt many of them are going to require a PHP cert. As for client gigs, I prefer to show clients the work I've already done. To them, the cert is meaningless. But seeing an actual site you've built means you really can do the work.
But if the company you're at doesn't mind paying and letting you take it, there's absolutely no reason to turn it down.
