Se lo metto come

function UpdateNews($data, $titolo, $testo, $id)
{
$strSql = "Update news SET data='".$data."', titolo='".$titolo."', testo='".$testo."'";
$strSql = $strSql . " WHERE id = " . $id;
var_dump($id);
return $strSql;
}

Esce...

NULL
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1