Check whether the XML prolog works.

>>>>templates/test.tpl
<?xml version="1.0" ?>
<!DOCTYPE foo [ <!ELEMENT note (bar)>
<!ELEMENT bar (#PCDATA)> ]>
<foo>
  <bar>...</bar>
</foo>

>>>>data.php
$this->tpl->prologRequired = false;

>>>>expected.txt
OUTPUT

>>>>result.txt
<?xml version="1.0" ?>
<!DOCTYPE foo [ <!ELEMENT note (bar)>
<!ELEMENT bar (#PCDATA)> ]>
<foo>
  <bar>...</bar>
</foo>