What is the difference  in php5 between $this and &$this
<p>I have some confusion about $this and &amp;$this, please describe this point .</p>

<h3>Update:</h3>

<p>Thanks for reply.  I know about pass by value and pass by reference. Please see the following program.</p>

<pre><code>/////////////////////////////////////////////////////
class my_class
{
    var $my_var;
    function my_class ($var)
    {
        global $obj_instance;
        $obj_instance = $this;
        $this-&gt;my_var = $var;
    }
}
$obj = new my_class ("something");
echo $obj-&gt;my_var;
echo $obj_instance-&gt;my_var;
////////////////////////////////////
</code></pre>

<p>In this program <code>$obj_instance = $this;</code> is copy the variable but output of this somethingsomething but when I am using  <code>$obj_instance = &amp;$this;</code> the output is somethings.  Why is it different?</p>

<p>Thank you.</p>
