A new and updated version of the Zend PHP Certification is on the way and will be available starting August, 31st:
Zend PHP 5 Certification Page
It's a complete rewrite, but the exam will still (as with the PHP 4 exam) cover 70 questions in 90 minutes. A new Study Guide will be available starting September and current PHP 4 certified people will get a discount for the PHP 5 exam.
To get detailed information, you can also listen to the Webcast Recordings at the phparch.com website.
And for those who prefer taking a MySQL 5 certification, there's also information available for you :-).