<?php
ob_start();
?>
<html>a html document</html>
<?php
$html = ob_get_clean();
// Specify configuration
$config = array(
'indent' => true,
'output-xhtml' => true,
'wrap' => 200);
// Tidy
$tidy = new tidy;
$tidy->parseString($html, $config, 'utf8');
$tidy->cleanRepair();
// Output
echo $tidy;
?>