[NiteWave]

hi, it took me much time to set up the test environment.

initially, same result as before -- but figured out it's because of xcache 2.0.1. it just ignore
xcache.var_namespace_mode = 2
xcache.var_namespace = "gid"

finally build latest php 5.4.11 + xcache 3.0.1, yes, just what we want!
in step 3, the output is

gid=uid=507(lstest3) gid=503(lstest3) groups=503(lstest3)

mona_test150112 is not set.

same as step 1.

this is a good news -- to summary in short:
lsphp5 suExec daemond + xcache 3.0.1, all users on a shared host can use opcode cache and variable cache in memory, and can't access each other's variables.
in php.ini, xcache.var_namespace_mode should set to 2:

; mode:0, const string specified by xcache.var_namespace
; mode:1, $_SERVER[xcache.var_namespace]
; mode:2, uid or gid (specified by xcache.var_namespace)
xcache.var_namespace_mode = 2
xcache.var_namespace = "gid"