What is wrong with this PhP code of checking NULL
<pre><code>static $result = NULL;

if  (!isNull($result))
{
    return $result;
}
</code></pre>

<p>This is a lazy loading pattern. I initialized the $result to NULL. Then I check if it's NULL. If it is, compute data.</p>

<p>Well the program crash at that line. Also isNull($result) yields null, rather than true or false.</p>

<p>What's the problem?</p>
