PHP Manual PHP at the Core: A Hacker's Guide Zend Engine 1 ZEND_JMP_SET Old introduction Zend Engine 1 Table of ContentsOld introductionStreams API for PHP Extension AuthorsZend API: Hacking the Core of PHPTSRM API Zend Engine 1 is the internal engine used by PHP for the entire version 4 release line. It is no longer considered active, but the old ZE1 documentation is preserved here exactly as it was.