it may be almost useless to use xcache var under php suExec
opcode cache is associated with a php process, web server start/stop the php process dynamically. 2 consecutive requests from a user may be served by different php process. that means cached var in previous request can't be referenced in current request.
if php process fork sub process, then cached var can be shared between these parent/child process. otherwise, cache can't be shared between php process -- not say it's impossible in principle, but it's the status of current top 3 implementation of opcode cache: APC, eAccelerator, XCache