( string user, string password [, string database [, resource link_identifier]] )
mysql_change_user() changes the logged in user
of the current active connection, or the connection given by the
optional link_identifier parameter. If a
database is specified, this will be the current database after
the user has been changed. If the new user and password
authorization fails, the current connected user stays active.
This function is deprecated and no longer exists in PHP.