$a = 5; $b =& $a; echo $a; echo '<br />'; echo $b; unset($a); echo $a; echo '<br />'; echo $b;
5 5 5
$a = 5; $b =& $a; echo $a; echo '<br />'; echo $b; $a = ''; echo $a; echo '<br />'; echo $b;
5 5