(PHP 4, PHP 5)
posix_setgid — Set the GID of the current process
Set the real group ID of the current process. This is a privileged function and needs appropriate privileges (usually root) on the system to be able to perform this function. The appropriate order of function calls is posix_setgid() first, posix_setuid() last.
Note: If the caller is a super user, this will also set the effective group id.
The group id.
如果成功则返回 TRUE，失败则返回 FALSE。
Example #1 posix_setgid() example
This example will print out the effective group id, once it is changed.
<?php
echo 'My real group id is '.posix_getgid(); //20
posix_setgid(40);
echo 'My real group id is '.posix_getgid(); //40
echo 'My effective group id is '.posix_getegid(); //40
?>