Raphael Stolt, in working on his component for the Zend Framework (based on the PHP_CodeSniffer PEAR package), pulled together all of the information Zend provides about their coding standards into one place.
Before jumping into the development of a Zend Framework coding standard for the PHP_CodeSniffer Pear package, I spent some time revisiting and compiling the available Zend Framework coding standards into a handy one-paged Pdf document.
You can download the file here or, if you want something a bit more "spread out", check out the coding standards on the Zend Framework website.