We have a VB application that needs to run an specific flow on a PHP page. This application was correctly catching the PHPSESSID cookie and using it for all subsequent requests. However, PHP wasn't able to restore any changes made on $_SESSION variable. The variable was changed, saved, and on the next request it was restored as an empty array. We found out that changing the Connection header from "Keep-Alive" to "Close" fixed the issue. I couldn't find anything on the web saying that PHP sessions shouldn't be restored under Keep-Alive connections. Does anyone know why this was happening? PS: We didn't find anything weird or different on Apache, ModSecurity or PHP configuration settings.