php simple test

<?php
class a{
        public $a = 'cc';
}

$a = new a();
$b = $a;

--------

$a->a  = 'xx';

echo $b->a;

--> xx

$b->a  = 'rr';

echo $a->a;

--> rr

unset($a);

echo $b->a;

--> rr

--------------

$c = null;

var_dump(isset($c));

unset 和 =null的区别

<?php
$b = 1;

$a =& $b;
------------

$a = null;
echo $b;

-->null

unset($a);
echo $b;

--> 1