passing a function as a string in php
<p>I'm just starting to learn PHP and am using the W3 Schools tut. In the error handling section there is this code:</p>

<pre><code>&lt;?php
function customError($errno,$errstr) {
    echo '&lt;b&gt;Error:&lt;/b&gt; [$errno] $errstr&lt;br /&gt;';
}
set_error_handler('customError');

echo($test);
?&gt;
</code></pre>

<p>Why is the customError() function being passed as a string? Is this a mistake in the tut?
Also, why isnt <code>$test</code> defined?</p>
