<?php
$html_string = '<div id="myelementID" class="hello" data-foo="bar">...</div>';

$dom = new DomDocument;
$dom -> loadHTML($html_string);
$el = $dom -> getElementById("myelementID");

if (!empty($el))
{
	$elemString = "<div";
	foreach ($el -> attributes as $attr) 
	{
		$name = $attr -> nodeName;
		$value = $attr -> nodeValue;	
		$elemString .= " {$name}=\"{$value}\"";
	}
	$elemString .= ">";
	echo $elemString;
}