php-cgi is an old and usually quite unencouraged way to deploy PHP; the vulnerability that we think took down the forums (and which the wiki was susceptible to) only applied to it, for example. The standard way, with Apache, is to use mod_php, though there may be a reason we aren't (I've heard of concerns about running e.g. {some jpg image which exploits a PHP flaw}.php.jpg accidentally as PHP by this route). A more modern way, which certainly alleviates the concerns I mention (and to boot, it's what I use for my own PHP deployments), is to use nginx with fcgi backed by php-fpm. We may not want to change existing things, but as we update we may want to migrate slowly to a more modern PHP deployment scheme.