Given that $var = 1, how come $var = $var === 0 doesn't return false?
<p>Firstly, I am dealing with 1s and 0s here and I'm well aware that 1 == true and 0 == false. However I'm curious as to why this doesn't work:</p>

<pre class="lang-php prettyprint-override"><code>$var = 1;
echo $var; /* 1 */
$var = $var === 0;
echo $var; /* Nothing */
</code></pre>

<p>Is there a reason the second instance of <code>echo $var;</code> isn't returning 0 (false) and instead returns nothing?</p>

<p>Equally, <code>!$var</code> also returns nothing. What is causing this behaviour?</p>
