That seems to be the correct config to symply tidy an HTML fragment (in a valid XHTML syntax) :
<?php
$tidy_config = array(
'clean' => true,
'drop-proprietary-attributes' => true,
'output-xhtml' => true,
'show-body-only' => true,
'word-2000' => true,
'wrap' => '0'
);
?>