Why is it that I can't reference a global variable directly in PHP?
<p><strong>I'm curious to know why the following code behaves differently?</strong></p>

<p><em>The following does not work:</em></p>

<pre><code>$_variable &amp;= global $_global;
echo $_variable;
</code></pre>

<p><em>The following works:</em></p>

<pre><code>global $global;
$_variable &amp;= $_global;
echo $_variable;
</code></pre>

<p>?</p>
