Description:
------------
Hi. After upgrading from PHP 4.3.11 to 4.4.0 I get the 
famous "Only variable references should be returned by 
reference" notice in one of my projects. The function in 
question returns by reference, but only needs to do this 
sometimes. Other times, it returns nothing at all, because 
the caller does not need a return value. In these latter 
cases, PHP produces the notice as of 4.4.0.

This surprised me because it's perfectly fine to have a 
normal return-by-copy function that does not return 
anything. So why not a return-by-reference function?

I couldn't find any documentation that if your function 
returns by reference, then you must always return something.

In my particular case I can rewrite the function so that it 
always returns something, even when the caller has no use 
for it. I just wasn't sure if the notice in this case was 
intended, and if so, why.

If the behavior is intended, then the documentation should 
reflect this.

Reproduce code:
---------------
error_reporting(E_ALL);

function &foo_by_reference_with_return() {
	echo __FUNCTION__ . "<br />\n";
	return $GLOBALS['bar'];
}
function &foo_by_reference_without_return() {
	echo __FUNCTION__ . "<br />\n";
} // line 11
function foo_by_copy_with_return() {
	echo __FUNCTION__ . "<br />\n";
	return $GLOBALS['bar'];
}
function foo_by_copy_without_return() {
	echo __FUNCTION__ . "<br />\n";
}

foo_by_reference_with_return();
foo_by_reference_without_return(); // causes notice in 4.4.0
foo_by_copy_with_return();
foo_by_copy_without_return();

Expected result:
----------------
foo_by_reference_with_return
foo_by_reference_without_return
foo_by_copy_with_return
foo_by_copy_without_return

Actual result:
--------------
foo_by_reference_with_return
foo_by_reference_without_return
Notice: Only variable references should be returned by 
reference in references.php on line 11
foo_by_copy_with_return
foo_by_copy_without_return