phpDocumentor输出参数

I've got a block of code which was written a while ago and I'm looking to document, but one of the functions has an output parameter - how should a phpDoc-block be written to specify that a parameter is an output parameter?

Note - this isn't "I love output parameters" or "I want to use them", it's "They were used, how are they documented?" :P

Just in case I've got the name of them wrong, something like this:

function foo (&$bar)
{
    $bar = 1;
    return 2;
}

$varIs2 = foo($varIs1);
echo $varIs1; // 1
echo $varIs2; // 2

I'd use:

@param    integer    &$bar    value to be reset

with the & in the param block