php tidy strange behaviour

Asked 26/7, 2012 at 13:14 Answered 2/8, 2012 at 10:54

I'm using php's tidy library to "clean and repair" some html coming from user input.

Everything works fine, but i'm running into a problem that I can't figure out what its cause is. My code is like this:

$tidy = new tidy();

    $tidy_options = array(
        'hide-comments' => true,'tidy-mark' => false, 'indent' => false,
        'new-blocklevel-tags' => 'article,footer,header,hgroup,output,progress,section,video',
        'new-inline-tags' => 'audio,details,time,ruby,rt,rp',
        'drop-empty-paras' => false, 
        'doctype' => '<!DOCTYPE HTML>',
        'sort-attributes' => 'none', 'vertical-space' => false,
        'output-xhtml' => true,'wrap' => 180,
        'wrap-attributes' => false,
        'break-before-br' => false,
        'show-body-only' => true
        );
$data = $tidy->repairString($data, $tidy_options, 'UTF8');
echo $data;

This works for all kinds of input, except when i'm trying to use html for embeding swf files.
So , i try this code:

<object data="http://the_swf_file_url" type="application/x-shockwave-flash" width="853" height="520"> 
    <param name="movie" value="http://the_swf_file_url"> 
</object>

but repairString stripes off all of it, and returns an empty string.
The strangest thing is that:
-If i enter some text along with the above, so the input is like Hello world<object...>...</object> then it works fine.
-Or if i specify 'show-body-only' => false it also works fine!

Any clue Why this is happening? Thanks in advance.

Edit: tried pankar's suggestion with setting preserve-entities to true but had no luck...

Barbette answered 26/7, 2012 at 13:14 Comment(0)

The problem is that you are trying to process an HTML fragment.

When you do this, the rest of the document is inferred. If you leave the configuration as default, and output a tidy document with just a piece of text, you will see the DOCTYPE, html, head and body tags that you did not give it. It inferred that these tags had to exist.

The problem here is that the HTML specification regarding objects states that:

The OBJECT element may also appear in the content of the HEAD element.

When the location of your fragment is being inferred, it puts it in the first place that it can occur. This means that tidy will place it in the head tag.

The reason why show-body-only is affecting your output is because your fragment did not get placed in the body.

However when you add some text, it forces your snippet into the body tag. This is because raw text is not allowed in the head tag. So the logically inferred location of your fragment is in the body.

In my opinion, the best option available to you is to inject all of your code fragments into a "template" document, and then parse them out again afterwards. You can probably do this fairly easily with DOMDocument.

A second solution would be to inject a sentinel value that you can strip out again afterwards, when showing only the body.

I.e.

____MY_MAGIC_TOKEN____
<object ...></object>

Then you can strip it out again afterwards.

Abc answered 2/8, 2012 at 10:54 Comment(2)

Hi Leight, thanks for bothering with my question, and for offering an explanatory enough answer. Now i get the issue, and can provide myself with a fix (both your proposals seem legit). I could've never thought that The OBJECT element may also appear in the content of the HEAD element. – Barbette 7/8, 2012 at 20:21

No problem, standards are tricky buggers. Everyone wants to stick to them, but most people don't know (or care) what's in them. After some experimenting and a "wtf" moment, I had to look it up myself to be sure! – Abc 7/8, 2012 at 20:28

~~Try specifying the configuration option preserve-entities to true (is defaulted to false).~~

EDIT

Seconds (more thorough) thoughts. This is an expected behavior. By setting show-body-only to true you tell tidy to output the body part of the xhtml processed document.

This setting will actually ignore everything in the <head> of the document. <object> component is a child of <head>. You can verify this by simply specifying

$data = "<title>My Site</title>".

The output again will be blank.

Your attempt to put prefixed text to <object> tag simply tricks tidy as it comes to believe that this data has to be handled as part of the body of the page and thus to be displayed.

Hope it helps more this time.

Inundate answered 26/7, 2012 at 13:28 Comment(3)

Hi pankar, thanks for replying. I tried your suggestion but had no luck again. Does this mean tidy thinks that my code <object>... is not well-formed entitities? why then if i enter some other text along with my object code it works fine? – Barbette 26/7, 2012 at 13:31

Pankar, thanks again for bothering with my question. I understand the 'show-body-only' => true part you describe, that's the needed behaviour. What I don't get is that "<object> component is a child of <head>"! Am i missing something really important like this? I can't find any documentation verifing your claim. Of course, if this is really true, then the solution to my question is obvious. Could you please elaborate on this a bit more? Thanks a lot for your time! :) – Barbette 26/7, 2012 at 23:26

I understand your concerns and I know that this doesn't make sense but it seems that it's a limitation of tidy (probably considers it metadata information that needs to be placed on head?). I end up to believe that this is a bug! – Inundate 27/7, 2012 at 8:21

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