yes, running PHP as a CGI script would allow the script to be run under the users uid/guid since you are using SuExec, but if you want to run mod_php (or mod_perl) scripts under a specific UID/GID your best (only) plan is to create a seperate httpd instance for this user - this provides the strictest security although it does require some manual configuration and you probably don't want to create a ton of these individual user specific httpd processes.