Getting and echo element including content by ID using PHP - php

Question

I am trying to get an element from external page (div tag including some content) by its ID and print it to another page on a site. I am trying to use the code below however getting tag errors which I have in the including element (figcaption, figure). Is there anyway to include only a single div by its ID from another page?
PHP
$doc = new DOMDocument();
$doc->loadHTMLFile($_SERVER['DOCUMENT_ROOT'].'/assets/includes/example.html');
$example = $doc->getElementById('test');
echo $example->nodeValue;
?>
HTML
<div id="test">
<figure>
<img src="img1.jpg" alt="img" />
<figcaption></figcaption>
</figure>
</div>

Answer 1

DOMDocument output errors on HTML5 even if there are not error, due to impossibility of DTD check.
To avoid this, simply change your code in this way:
libxml_use_internal_errors( True );
$doc->loadHTMLFile( '$_SERVER['DOCUMENT_ROOT'].'/assets/includes/example.html' );
Anyway — even if some errors are displayed — your code load correctly HTML document, but you can't display the <div> because you use a wrong syntax: change echo $example->nodeValue
with:
echo $doc->saveHTML( $example );
The right syntax to print DOM HTML is DOMDocument->saveHTML(), or — if you want print only part of document — DOMDocument->saveHTML( DOMElement ).
Also note that DOMDocument is designed to not try to preserve formatting from the original document, so you probably don't obtain this:
<div id="test">
<figure>
<img src="img1.jpg" alt="img" />
<figcaption></figcaption>
</figure>
</div>
but this:
<div id="test">
<figure><img src="img1.jpg" alt="img"><figcaption></figcaption></figure>
</div>

Answer 2

You are currenlt only echo-ing node value, which will be text. Since you have no text in #test, nothing will output.
You have to print it as HTML:
echo $doc->saveHTML($example);