the cause is that he has tried to pass by reference at 'call-time' i.e. when he calls a function he has already defined. To solve it you need to tell PHP that you will be passing by reference in the function declaration and not in the call:
function test(&$arg1, &$arg2)
also the refernece operator (&) has been depreciated for the 'new' keyword, and i believe that PHP now automatically passes objects around by reference.
mysql> SELECT * FROM `users` WHERE `users`.`clue` > 0;
Empty set (0.00 sec)