as far as im aware zend is available for php which will achieve the same thing.
check your phpinfo (create a file phpinfo.php with the following)
// Show all information, defaults to INFO_ALL
phpinfo();
// Show just the module information.
// phpinfo(

yields identical results.
phpinfo(INFO_MODULES);
?>
if it reads
This program makes use of the Zend Scripting Language Engine:
Zend Engine v1.2.0, Copyright © 1998-2002 Zend Technologies
with Zend Optimizer v2.0.1, Copyright © 1998-2002, by Zend Technologies
Then you have zend installed.
Oh yeah its only the optimizer....