The folks over at php|architect have release another resource to help get you certified as a Zend Certified Engineer - the Zend PHP 5 Certification Study Guide.
php|architect's Zend PHP 5 Certification Study Guide, edited and produced by the publishers of php|architect, provides the most comprehensive and thorough preparation tool for developers who wish to take the exam.
This book provides complete coverage of every topic that is part of the exam, for more information, see the chapters & source code.
Chapters for the book cover topics like the PHP basics, Strings and Patterns, Object Oriented Programming, Security, and XML/Web Services. Check out this sample chapter to get a taste of what's inside.