Description:
------------
When calling posix_get[e]gid() to drop root privledges, it does NOT logout of group=0(root).

Please look VERY closely at the 'id' output from the script, you will see that the third section "groups=" shows that i am effectively still logged into group "0".

It indeed sets the current process group id to 0, however, it does NOT completely DROP all group memeberships, as well PHP provides no "posix_initgroups()" so there is no way to call initgroups() on linux to re-init the group memeberships from /etc/group, which would effectively, or should, drop the group=0(root) membership.

Reproduce code:
---------------
<?
 system("id");
 posix_setgid(500);
 posix_setegid(500);
 posix_setuid(500);
 posix_seteuid(500);
 system("id");
?>

Expected result:
----------------
[root@admin cluster]# php test.php
uid=0(root) gid=0(root) groups=0(root)
uid=500(cluster) gid=500(cluster) groups=500(cluster)
[root@admin cluster]#

Actual result:
--------------
[root@admin cluster]# php test.php
uid=0(root) gid=0(root) groups=0(root)
uid=500(cluster) gid=500(cluster) groups=0(root)
[root@admin cluster]#