How can you pass an argument by reference when defining a function?

How can you pass an argument by reference when defining a function?

function doSomething$($@value$\_$by$\_$reference$)\{//$ code $\}$

function doSomething$($&$value$\_$by$\_$reference$)\{//$code $\}$

Passing an argument by reference is not possible with PHP$.$

function doSomething$($$value$\_$by$\_$reference$)\{//$code $\}$