从亚马逊网页抓取特定图像

Question

I'm trying to scrap the data-old-hires and data-a-dynamic-image element from the below source:

<img alt="Honeywell Long-Life Pure HEPA QuietCare Air Purifier, 17000" 
src="http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SX425_.jpg"
data-old-hires="http://ecx.imagesamazon.com/images/I/61qtgZMjVDL._SL1280_.jpg" class="a-dynamic-image  a-stretch-vertical" id="landingImage" 
data-a-dynamic-image="{&quot;http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SX466_.jpg&quot;:[466,466],&quot;http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SX425_.jpg&quot;:[425,425],&quot;http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SY450_.jpg&quot;:[450,450],&quot;http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SX522_.jpg&quot;:[522,522],&quot;http://ecx.images-amazon.com/images/I/61qtgZMjVDL._SY355_.jpg&quot;:[355,355]}" style="max-height: 416px; max-width: 416px;">

But I'm getting an error stating that old and hires which belong to data-old-hires are undefined variables. Kindly help me retrieve data-old-hires and data-a-dynamic-image elements.

Here is the code:

$html  = file_get_html($url);
foreach($html->find('img[alt="Honeywell Long-Life Pure HEPA QuietCare Air Purifier, 17000"]') as $element) {
  //echo $element->src . '<br>';
  echo $element->data-old-hires.'<br>';
  echo $element->data-a-dynamic-image.'<br>';
}