<?php
$a = 1;

/**** Look at memory ****/

/*
 _________________________________________
|pointer | value |       variable's       |
 -----------------------------------------
| 1      |  1    |     $a                 | 
 -----------------------------------------  */

$b =& $a;

/*
 _________________________________________
|pointer | value |       variable's       |
 -----------------------------------------
| 1      |  1    |     &a, $b             | 
 -----------------------------------------  */

unset($a); 

/*
 _________________________________________
|pointer | value |       variable's       |
 -----------------------------------------
| 1      |  1    |     $b                 | 
 -----------------------------------------  */

     
printf("Variable b is pointing to the pointer 1 which value = %d",$b);

?>