Description:
------------
I see value in adding two functions to php: coalesce() and coalesce_strict(). 

Both of these would take an arbitrary number of arguments, and use the first non-empty() or non-null value (respectively).

For example:

$username = coalesce($_POST['username'], $_COOKIE['username'], 'guest');

Parameters passed would not have to be defined (eg, the above script should not generate notices if E_STRICT is on and $_POST['username'] is undefined), and undefined variables would be treated as null. 


Reproduce code:
---------------
// The PHP (close) equivalents:
function coalesce() {
	$max = func_num_args();
	for ($i = 0; $i < $max-1; $i++) {
		$value = func_get_arg($i);
		if (!empty($value)) {
			return $value;
		}
	}
	return func_get_arg($max-1);
}
function coalesce_strict() {
	$max = func_num_args();
	for ($i = 0; $i < $max-1; $i++) {
		$value = func_get_arg($i);
		if ($value !== null) {
			return $value;
		}
	}
	return func_get_arg($max-1);
}

Expected result:
----------------
coalesce('',0,1); // returns 1
coalesce(0,null,false,''); // returns '' (last value)
coalesce_strict(0,null,false,''); // returns 0