Nope, that's HTML/CSS I think..
Here's some PHP:
function template_main()
{
global $context, $settings, $options, $txt, $scripturl;
echo '
<div style="padding: 3px;">', theme_linktree(), '</div>
<table width="100%" cellpadding="3" cellspacing="0" border="0" class="tborder">
<tr>
<td align="left" class="catbg" width="100%" height="30">
<b>', $txt[139], ':</b> ', $context['page_index'], '
</td>
</tr>
</table>
<br />';
Parts of it look like html. That is because the PHP code is generating a html page each time it is viewed, so the html stuff and appropriate variables are echoed into a big long string which forms the html file.
This is part of the forum code by the way. :>