... Prev . ... References Explained . ... function foo (&$var) { $var =& $GLOBALS["baz"]; } foo($bar); . What happens is that $var in foo will be bound with $bar in caller, but then it will be re-bound with $GLOBALS["baz"] . There's no way to bind $bar in the calling scope to something else using the reference mechanism, since $bar is not available in the function foo (it is represented by $var , but $var has only variable contents and not name-to-value binding in the calling symbol table). ...