Stange behavior when increment value
<p>Here is my code </p>

<pre><code>$f1  = 1;
$f2  = ++$f1;
$f3  = ++$f2;
$f4  = ++$f3;

echo  $f1 . '&lt;br /&gt;'.$f2.'&lt;br /&gt;'.$f3.'&lt;br /&gt;' .$f4. '&lt;br /&gt;';
</code></pre>

<p>Output is:</p>

<pre><code>2
3
4
4
</code></pre>

<p>I expected $f4 value to be 5, but it is 4. 
What I miss ?</p>
