DomDocument and special characters
Try to set the encoding type after you have loaded the HTML.
$dom = new DOMDocument();
$dom->loadHTML($data);
$dom->encoding = 'utf-8';
echo $dom->saveHTML();
Other way
Solution:
$oDom = new DOMDocument();
$oDom->encoding = 'utf-8';
$oDom->loadHTML( utf8_decode( $sString ) ); // important!
$sHtml = '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">';
$sHtml .= $oDom->saveHTML( $oDom->documentElement ); // important!
The saveHTML() method works differently specifying a node.
You can use the main node ($oDom->documentElement) adding the desired !DOCTYPE manually.
Another important thing is utf8_decode().
All the attributes and the other methods of the DOMDocument class, in my case, don't produce the desired result.