The function result_dump_mem has a problem with the meta content type tag. It outputs it like this:
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
which is not correct X(HT)ML, because it closes with '>' instead of with '/>'.
A way to get the output correct is to use instead of result_dump_mem :
$domHtmlText = $domTranObj->html_dump_mem();
or, as a second alternative:
$domHtmlText = $domTranObj->dump_mem(true);