DOM document character error - php

Question

The character encoding of the HTML document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. The character encoding of the page must be declared in the document or in the transfer protocol.
dom create error like above,, and page return blank when I create new element in meta and data node like this :
<?php
$this->module->daftarkanJs('underscore-min.js');
$form = CJSON::decode(file_get_contents(Yii::app()->getBaseUrl(true).'/index.php/odk/api/index/id/'.$_GET['id']));
$input = CJSON::decode(file_get_contents(Yii::app()->getBaseUrl(true).'/index.php/odk/api/input/id/'.$_GET['id']));
function haveChild($id, $input_id){
$child = CJSON::decode(file_get_contents(Yii::app()->getBaseUrl(true).'/index.php/odk/api/child/id/'.$id.'/parentId/'.$input_id));
if($child['result']){ // jika child ada
foreach($child['result'] as $data){
// echo '- <b>'.$data['input_id'].'</b><br/>';
haveChild($id, $data['input_id']);
}
return true;
}else{
return false;
}
}
function loop($inputResult, $id){
$dom = new DOMDocument('1.0', 'utf-8');
$dom->preserveWhiteSpace = false;
$dom->formatOutput = true;
$html = $dom->createElementNS('http://www.w3.org/2002/xforms', 'h:html');
$html->setAttributeNS('http://www.w3.org/2000/xmlns/' ,'xmlns:h', 'http://www.w3.org/1999/xhtml');
$html->setAttributeNS('http://www.w3.org/2000/xmlns/' ,'xmlns:ev', 'http://www.w3.org/2001/xml-events');
$html->setAttributeNS('http://www.w3.org/2000/xmlns/' ,'xmlns:xsd', 'http://www.w3.org/2001/XMLSchema');
$html->setAttributeNS('http://www.w3.org/2000/xmlns/' ,'xmlns:jr', 'http://openrosa.org/javarosa');
$html = $dom->appendChild($html);
$head = $dom->createElement('h:h');
$head = $html->appendChild($head);
$title = $dom->createElement('h:t', 'xxxxxxx');
$title = $head->appendChild($title);
$model = $dom->createElement('m');
$model = $head->appendChild($model);
$instance = $dom->createElement('instance');
$instance = $model->appendChild($instance);
$data = $dom->createElement('data');
$data = $instance->appendChild($data);
$meta = $dom->createElement('meta');
$meta = $data->appendChild($meta);
$instanceID = $dom->createElement('instaceID');
$instanceID = $meta->appendChild($instanceID);
$bind = $dom->createElement('bind');
$bind->setAttribute("nodeset","/data/meta/instanceID");
$bind = $model->appendChild($bind);
foreach($inputResult as $data){
if(!$data['parent_id']){ // ambil yang bukan child
$check = haveChild($id, $data['input_id']);
if(!$check){
$data = $dom->createElement('data');
$data = $instance->appendChild($data);
$meta = $dom->createElement('meta');
$meta = $data->appendChild($meta);
$bind = $dom->createElement('bind');
$bind->setAttribute("nodeset","/data/".str_replace(" ", "_", $data['name']));
$bind = $model->appendChild($bind);
}
}
}
$body = $dom->createElement('h:b');
$body = $html->appendChild($body);
printf ("<pre>%s</pre>", htmlentities ($dom->saveXML()));
}
loop($input['result'], $_GET['id']);
?>

Answer 1

error in this line :
$data = $dom->createElement('data');
$data = $instance->appendChild($data);
$meta = $dom->createElement('meta');
$meta = $data->appendChild($meta);

Answer 2

You don't output the XML, but HTML with escaped XML.
<pre>some escaped xml</pre>
This output matches the error message if it is treated as XML. Here is no XML declaration with an encoding.
Stripped down to the DOM methods, your source outputs an XML document: https://eval.in/private/1507ef8a4065d0.
However, I suggest to use createElementNS() for ALL namespaced nodes. Calls like $dom->createElement('h:h'); are ambiguous.
$xmlns = [ 'h' => 'http://www.w3.org/1999/xhtml' ];
$dom = new DOMDocument();
$html = $dom->appendChild(
$dom->createElementNS($xmlns['h'], 'h:html')
);
$head = $html->appendChild($dom->createElementNS($xmlns['h'], 'h:head'));
echo $dom->saveXml();
Output:
<?xml version="1.0"?>
<h:html xmlns:h="http://www.w3.org/1999/xhtml"><h:head/></h:html>