My USP upgraded their systems with Zend Optimizer and actually created this problem initially. Spent hours with them doing the tweaking with code in my PHP.ini file so that it read properly but nothing they did corrected the problem.
They say it has to do with wordpress itself. Now all the other pages load just fine - it's only the home page that does not. Here's a little dialoge on what we did to correct:
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We're sorry for the confusion. I do see that error in your PHP error logs. We have an article in our knowledge base that addresses this issue (http://helpdesk.bluehost.com/index.php/kb/article/000303). It says:
If you are having a problem with the Zend Opimizer please ensure the file called php.ini contains the following lines.
[Zend]
zend_extension="/usr/local/Zend/lib/Optimizer-3.3.9/php-5.2.x/ZendOptimizer.so"
I checked the coding of your php.ini and it does not have this line of code in it. If you update your php.ini file to use the above code, it should resolve the error that is showing up related to Zend Optimizer.
1. Log into http://www.Bluehost.com.
2. Click on File Manager and choose Web Root.
3. Navigate to the directory your program uses for it's php.ini. This is generally the public_html directory, which should already be open.
4. Right click on the php.ini file and select Code Edit.
5. Enter the following code, starting with [Zend], at the bottom of the page.
Because Zend Optimizer has been standardized on all our servers, so that varying versions do not cause conflicting PHP.INI files, make sure your [Zend] portion appears as below in your PHP.INI:
[Zend]
zend_optimizer.optimization_level=15
zend_extension_manager.optimizer=/usr/local/Zend/lib/Optimizer
zend_extension_manager.optimizer_ts=/usr/local/Zend/lib/Optimizer_TS
zend_extension=/usr/local/Zend/lib/ZendExtensionManager.so
zend_extension_ts=/usr/local/Zend/lib/ZendExtensionManager_TS.so
If needed you can set your entire account to use the php.ini file in your public_html directory for all php.ini calls. This is done with the PHP Config tool in your cPanel by choosing the PHP5 (Single php.ini) option.
Finally it may still be necessary to copy the php.ini file into the folder your script is stored in or it's administration/configuration folder. You'll need to consult the script's documentation to find the needed location.
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All of this has been done and by them (Bluehost).
What can you offer as to correcting this in WordPress?