why there is a difference between below given output?
<pre><code>$y = 07;
echo 'Y: '.$y; // result is 7
$y = 08;
echo 'Y: '.$y; // result is 0
</code></pre>

<p><a href="http://codepad.org/unsH35zN" rel="nofollow">view demo</a></p>

<p><em><strong>:EDIT:</em></strong></p>

<p>One more similar to that </p>

<pre><code>$y = 013;
echo $y + 5; //this result in 16
</code></pre>

<p>I can not figure it out how its ans is 16? Can any one help?</p>
