Check whether the XML prolog works. >>>>templates/test.tpl <?xml version="1.0" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <foo> </foo> >>>>data.php $this->tpl->prologRequired = false; >>>>expected.txt OUTPUT >>>>result.txt <?xml version="1.0" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <foo> </foo>