Quercus

Quercus is Caucho Technology's 100% Java implementation of PHP 5 released under the Open Source GPL license. Quercus comes with many PHP modules and extensions like PDF, PDO, MySQL, and JSON. Quercus allows for tight integration of Java services with PHP scripts, so using PHP with JMS or Grails is a quick and painless endeavor.

Quercus implements PHP 5 and is internationalization/localization (i18n/l10n) aware. Quercus natively supports Unicode and the new Unicode syntax of the up-and-coming PHP 6. Quercus implements a growing list of PHP extensions (i.e. APC, iconv, GD, gettext, JSON, MySQL, Oracle, PDF, Postgres, etc.). Many popular PHP applications will run as well as, if not better, than the standard PHP interpreter straight out of the box. The growing list of PHP software certified running on Quercus includes DokuWiki, Drupal, Gallery2, Joomla, Mambo, Mantis, MediaWiki, Phorum, phpBB, phpMyAdmin, PHP-Nuke, Wordpress, and XOOPS.

http://quercus.caucho.com/