Zendoptimizer on Joomla 1.5.20

Anyone know how to install Zend optimizer 3.3.9 on the Joomla 1.5.20 Jumpbox?
I have tried editing the php.ini file and adding the entry path to the ZendOptimizer.so file and rebooting but no go. I see that they no longer supply an install script. I also could not seem to restart the http service.
Any tips appreciated.

Issue Solved!

Turns out that you need to edit the /etc/php5/apache2/php.ini file not the /etc/php5/cli/php.ini file and add the entry
[ZEND]
zend_extension=/path to the so file/ZendOptimizer.so