https://evo.im/blog/best-practices/fixing-ajaxsubmit-500-errors-caused-by-missing-zend-files-in-evolution-cms.html
Fixing ajaxSubmit 500 Errors Caused by Missing Zend Files in Evolution CMS
Dec 17, 2014 - How to diagnose ajaxSubmit 500 errors when the plugin fails because a Zend dependency is missing.