PHP unset () function destroys variables but does not implement free memory

<?

$a = "Hello";
$b = & $a;
Unset ($b);
echo $a;    Output Hello
echo $b;    Error
$b = "123456";
echo $a;    Output Hello
echo $b;    Output 123456
echo "
$a = "Hello";
$b = & $a;
unset ($a);
echo $a;    Error
echo $b;    Output Hello
$a = "123456";
echo $a;    Output 123456
echo $b;    Output Hello
echo "
Conclusion:
The PHP unset () function is used to destroy variables, but in many cases, the function only destroys the variable, and the value of the variable stored in the memory is still not destroyed.
That's not going to get what we want to do to free up memory. You can use the $ variable =null method to release its memory or to have two variables unset ();

Http://www.cnblogs.com/ellisonDon/archive/2012/11/19/2777453.html

?>

PHP unset () function destroys variables but does not implement free memory