When this option is set to Yes (as it is by default), virtual server owners are allowed to edit their PHP configuration. However, you can set it to No to prevent this, either for security reasons or to prevent in-experienced admins from making incorrect changes.

This is implemented by making the domain's `~/etc/php.ini` file editable only by the `root` Unix user. Be aware that this is not a foolproof method of preventing changes to the PHP configuration though - the domain owner could still specify a different config file by editing the PHP wrapper scripts in `cgi-bin`, running their own copy of PHP, or running PHP scripts as CGI programs.