Apache2 MPM modules in General Discussions Posted October 5 It's not osCommerce that needs to be thread safe but PHP. See https://serverfault.com/questions/904065/switch-apache-from-prefork-to-event-in-ubuntu-16-get-php-7-working for more discussion. Note in particular that it switches from mod_php to the fast CGI PHP to use MPM Event. At this point, you should probably target Event over Worker. Both require a thread-safe PHP with only thread-safe PHP modules.