Stripping microdata from an XHTML with PHP - using RegEx?

Question

First: I've read the general; don't use RegEx on XHTML arguments like this one: RegEx match open tags except XHTML self-contained tags and I do understand how RegEx will fail on nested XHTML or XML nodes.

I don't see why manipulating attributes of an XML alone should break using RegEx. So there seems to be exceptions to the general rule. Attributes are always contained in a single node starting with a < and ending with a > any other < or > in between would break the XML so such can't occur.

Now I'd like to clean an XHTML string of any microdata it might contain. That is any attributes itemscope, itemtype, itemprop, itemid and itemref. Something like this:

...
<body itemscope="itemscope" itemtype="http://schema.org/WebPage">
<div itemprop="maincontent">content</div>
...

What's the best way to do this in PHP?

If you want to clean the microdata attributes out of HTML, then HTMLPurifier or htmltidy might suffice. Neither knows about the html5 attributes and will remove them. — mario
– mario, Commented Jun 19, 2011 at 19:54

Femi · Accepted Answer · 2011-06-19 20:06:20Z

4

I'd actually suggest:

Loading the string with something like SimpleXML.
Removing the attributes you are interested in flushing.
Saving it back to a string.

There are a bunch of namespace issues that I'm not sure how you'd have to handle, but that will probably be cleaner/happier than trying to build one or more regex expressions and make sure you don't miss anything.

EDIT: turns out SimpleXML won't work (limited modification capabilities) but DOM will. Something like this:

$data=<<<END1
<body itemscope="itemscope" itemtype="http://schema.org/WebPage">
<div itemprop="maincontent">content</div>
</body>
END1;

$xml=new DOMDocument();
$xml->loadXML($data);

// find every relevant node
$xpath = new DOMXPath($xml);
$attr = $xpath->query("//@itemscope|//@itemprop|//@itemtype");
foreach ($attr as $entry) {
  $entry->parentNode->removeAttribute($entry->nodeName);
}
echo $xml->saveXML();

You'd have to modify it to include all the attributes you want to remove, and like I said I have no clue how it would deal with namespaces, but its a start.

edited Jun 19, 2011 at 20:06

answered Jun 19, 2011 at 19:48

Femi

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4 Comments

C.O. Over a year ago

Looks great. One more thing, There can be meta tags in the body due to the microdata stuff. I thought I could select those with xpath 'body//meta' but somehow it does not work yet...

Femi Over a year ago

The query above works on attributes: I think you want to do //body/meta but also realize that since those aren't attributes you can't use removeAttribute on them. Easiest way would be to put tags in a separate xpath loop and use removeChild instead.

C.O. Over a year ago

that I understood. I did make it a separate xpath loop and did use removeChild. That's on the manual. $xml->getElementsByTagName("body")->item(0)->getElementsByTagName("meta")->length; gives back the actual number of tags while all xpath versions I tried even $xpath->query("//body")->length gives back 0. I was wondering what my xpath problem is. Trying the same with an attribute $xpath->query("//@itemscope")->length;works though...

Femi Over a year ago

Hard to tell exactly what you might be doing wrong without code, but $blk = $xpath->query("//meta"); forreach($blk as $t){ $t->parentNode->removeChild($t); } works for me.

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