PHP function - compare with the following examples
<ol>
<li>compare with the two similar examples and please tell me why?</li>
<li><p>please explain it clearly.</p>

<pre><code>function inc(&amp;$value, $amount = 1) {
    $value = $value + $amount;
    echo $value;    //21
}

$val = 20;
inc($val); 
echo "&lt;br&gt;$val";   //21

echo "&lt;hr&gt;";

function incSec(&amp;$value, $amount = 1) {
    $value = $value + $amount;
    echo $value;    //21
}

incSec($valSec = 20);   
echo "&lt;br&gt;$valSec";    //20
</code></pre></li>
</ol>

<p>I'm trying to test, but can't get the reason.</p>
