Pass-by-reference with default?

Unfortunately, in PHP, you don't appear to be able to use default argument values when passing by reference, so you can't make pass-by-reference arguments optional.

eg, you can write:

function secondargoptional($something,$otherthing='default') { ... }

or

function secondargbyreference($something,&$otherthing) { ... }

but not

function secondargopptionalbyreference($something,&$otherthing=NULL ) { ... }

which would allow me to append the reference parameter only when I actually need it.

(In PHP 4.3.4 at least)

Anyone got a workaround, or care to prove me wrong?