[wp-hackers] Replace default doctype on one page only through plugin

[Lynne Pope]

Thanks Chris.
Both your examples work perfectly, of course (in case anyone reading this
wants to know too).

I will be sending my validation fixes to the plugin developer and will
probably blog about the different ways of achieving doctype changes in the
header. Not including the last snippet though - as you say, ob_start can be
a dangerous thing.

If you are happy for me to use your filter code in my post, please let me
know - and also let me know which URL you would like me to link back to when
I give you credit.

Cheers,
Lynne


2009/1/19 Gaarai <gaarai at gaarai.com>

> The idea I sent before works, but it would require modification of the
> theme.
>
> The only way I can see of doing this completely inside the plugin with not
> modification of the theme itself is by using the ob_start() function.
>
> For example:
>
>   <?php
>       if ( *$contact_page_displayed* ) {
>           add_action( 'get_header', 'start_output_collection', 1000 );
>           add_action( 'wp_head', 'send_output', 1000 );
>       }
>
>       function start_output_collection() {
>           ob_start();
>       }
>
>       function send_output() {
>           $header = ob_get_contents();
>           ob_end_clean();
>
>           $header = preg_replace( '|<!DOCTYPE[^>]*>|i',
>   '*<!DOCTYPE..>*', $header );
>
>           echo $header;
>       }
>   ?>
>
> I've tested this on my test site, and it works.
>
> There are two places of interest that I have made bold.
>
> The first one will have to be replaced with logic that determines whether
> or not the contact form is rendered on that page or not. This is completely
> dependent upon exactly which plugin you are using.
>
> The second one is the actual doctype to be output. I know what you are
> going for, but I shortened it to make the code look better in the email.
>
> Now, you just sent a message about wanting a bulletproof way of doing it.
> The way I sent before is bulletproof as it will always work. The main issue
> with the code for mass distribution is the requirement to modify the theme.
>
> This solution /seems/ to be ideal then, but it is not. As for bulletproof,
> it definitely is not.
>
> The problem is that the ob_start function does not nest. There is no way to
> guarantee that nothing else will call ob_start between the
> start_output_collection() and send_output() functions. On a standard install
> with the default theme, there are a total of 45 apply_filters calls as well
> as requiring the theme's header.php code. At any point in executing any of
> these sections of code, some code may exist that makes use of ob_start.
>
> So, this solution may be useful to you with your own site, but I would not
> recommend it at all for general public use as ob_start should only be used
> in tightly-controlled sections of code where you know for a fact that there
> is no chance that another instance of ob_start will occur.
>
> In closing, you can do what you wish with this code, but I still recommend
> using the first set of code that I sent as it 1) won't cause site failure
> due to unknown code interfering with its operation and 2) won't cause other
> code to fail since it doesn't use the possibly-destructive ob_start
> function.
>
> Chris Jean
> http://gaarai.com/
> http://wp-roadmap.com/
>
>
>
> Lynne Pope wrote:
>
>> Well, what I am trying to do is this...
>>
>> I am using a contact form plugin on my contact page. I have cleaned up
>> XHTML
>> validation errors on the form but the form uses Recaptcha for anti-spam
>> assistance and the no-script fallback for Recaptcha is an iframe.
>>
>> Since DOCTYPE applies to the document and not to an overall site, I
>> decided
>> to get pendantic and change my XHTML 1.0 STRICT to XHTML 1.0 TRANSITIONAL
>> for that one page alone.
>> Now, for my own site I can simply make the contact page into a template
>> and
>> call a different header, but having got the bit between my teeth I decided
>> it would be more useful if I could find a way to add a DOCTYPE override to
>> the plugin.
>>
>> I didn't write the plugin (too lazy to write my own contact form) but
>> realise that if I have issues with validation for it then others will have
>> too. Ergo, if I can find a way to do this safely within the plugin itself
>> the code then becomes reusable and worth contributing back.
>>
>> I'm not going to hassle the plugin developer over this as I realise not
>> everyone cares if they have one page that doesn't validate. Besides, once
>> I
>> work out a way to do it without creating more than negligable performance
>> issues this will be something I can reuse.
>>
>> Lynne
>>
>> 2009/1/19 Mike Schinkel <mikeschinkel at newclarity.net>
>>
>>
>>
>>> Lynee:
>>>
>>> Does it even need to be in a plugin?  It this for this site only, or are
>>> you trying to create generic functionality?  Can't you do just do
>>> something
>>> like (in ~psudeo-code):
>>>
>>> <?php
>>>
>>> if ($_SERVER['REQUEST_URI']=='special_url') {
>>>  echo '<Special DocType>';
>>> } else {
>>>  echo '<Regular DocType>';
>>> }
>>>
>>> ?>
>>>
>>> -Mike Schinkel
>>> http://mikeschinkel.com/custom-wordpress-plugins/
>>>
>>>
>>> Lynne Pope wrote:
>>>
>>>
>>>> Hi all,
>>>> I am working on a site that is using XHTML 1.0 Strict but want to serve
>>>> XHTML 1.0 Transitional on one page only. The page uses a plugin so the
>>>> change to the doctype could go into the plugin.
>>>>
>>>> I can do a query in header.php but want to avoid unnecessary queries
>>>> (why
>>>> add an additional query to 300+ pages when only one is affected?) but
>>>>
>>>>
>>> cannot
>>>
>>>
>>>> get an override working for the plugin.
>>>>
>>>> Any ideas?
>>>>
>>>> Lynne
>>>>
>>>>
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