<p>Is it alright to do this?</p>

<pre><code>$author = strtolower($_SESSION['valid_username']);
</code></pre>

<p>I want to enter all authors into the table as lower case.</p>

Yes, that's fine as long as
```
$_SESSION['valid_username']
```
is set, otherwise you'll get a notice (if your error reporting is set that low).
You can check if it exists with
```
if (isset($_SESSION['valid_username']))
```