Are there any server configurations that can allow chmod to work for group members in PHP?

By default, PHP runs as the web server user (such as Apache or Nginx), which may not have the necessary permissions to change file permissions using chmod for group members. One way to solve this issue is by using the PHP function `posix_seteuid` to temporarily switch to a user with the appropriate permissions before calling `chmod`.

// Switch to a user with appropriate permissions
posix_seteuid(fileowner($file_path));

// Change file permissions
chmod($file_path, 0664);

// Switch back to the original user
posix_seteuid(0);