Description:
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I have the same problem with page from wikipedia. 

It seem that the loadhtml works with iso character in internal.

Same bug that bug #32547

Reproduce code:
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this code works :
		$url="http://".$lang.".wikipedia.org/wiki/".$article;
		$this->dom=new DomDocument('1.0', 'UTF-8');
		$str=file_get_contents($url);
		$this->dom->loadXML($str);
		$this->contenu = $this->dom->saveXml();
this code don't works :
		$url="http://".$lang.".wikipedia.org/wiki/".$article;
		$this->dom=new DomDocument('1.0', 'UTF-8');
		$str=file_get_contents($url);
		$this->dom->loadHtml($str);
		$this->contenu = $this->dom->saveXml();
It seem that the loadhtml works with iso characters in internal.

Expected result:
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Code with utf-8 encoded characters

Actual result:
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Code with bad characters