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I've just updated from 9.10 to 10.04. Everything seems to run fine except for zend optimizer which is throwing "Zend Optimizer not installed" error. I went to php.ini and the following line is still there Code:


Also I checked that the file does exist and that the php.ini I am looking at is in fact the php.ini file that is being used by the server. Please let me know if you have any ideas about how to fix or debug this.

Thanks, Eugene

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up vote 2 down vote accepted

Unfortunately Zend Optimizer isn't available for PHP 5.3 yet. You can read about it at the Zend forums: If you really need Zend Optimizer because of Zend Guarded PHP applications you will have to downgrade to PHP 5.2. Or if the application you need is available as an ionCube package you can try ionCube.

Original answer (this still applies for other versions or when a PHP 5.3 compatible version is released):

The PHP version in Ubuntu 10.04 is updated from 5.2.x (Ubuntu 9.10) to 5.3.x. Your Zend Optimizer extension is probably not working because it is outdated and not compatible anymore (if you haven't updated it in the meanwhile). Try to update your Zend Optimizer extension and check if it makes any difference.

If the config really is used by the server and the problem still exists after upgrading Zend Optimizer, check your Apache error_log for any problems loading the Zend Optimizer extension.

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Thanks for help! I enabled debug level of error logging and finally managed to see something. Here is the error "Zend Optimizer requires Zend Engine API version 220060519. The Zend Engine API version 220090626 which is installed, is newer. Contact Zend Technologies at for a later version of Zend Optimizer." I am not sure what to do with it though...should I downgrade zend engine? If yes, do you by chance have some manuals at hand? PS. I've double-checked and my is indeed the newest one – Eugene May 4 '10 at 21:54
I was wrong in my original answer, unfortunately Zend Optimizer isn't available for PHP 5.3 yet. – PowerSp00n May 4 '10 at 22:15
Yeah, you are right, I googled zend forums and found the same info. I'll be looking for a way to downgrade php now. Thanks for the help! – Eugene May 4 '10 at 22:46

Eugene, you should download Zend Guard for PHP 5.3 from the following page:

Pay attention to download the Linux version ;-)

Take the file and put it in:

Then, update your line in php.ini to look as follows:

Good luck!

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beta loader files available now for php 5.3 -

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