function set(&$x, &$y)
{
    $x =& $y[2];
}

$y = array(
    0,
    1,
    array('something')
);

$x = array('old_val');
print "1. inited, x is:n";
print_r($x);

set($x, $y);

print "n2. now, x is: ";
print_r($x);

1. inited, x is:
Array
(
    [0] => old_val
)

2. now, x is: Array
(
    [0] => old_val
)

function &set(&$x, &$y) {}

$x =& set($x,$y);

$x =& $y[2];