[pmwiki-devel] About categories

[Petko Yotov]

On 18/01/2025 21:45, Simon wrote:
> Category pages are perhaps the only time where PmWiki renders pages
> when they do not exist.

PmWiki renders the Site.PageNotFound text if any requested page doesn't 
exist, with a header "HTTP/1.1 404 Not Found".

For Category pages which does not exist, the Site.PageNotFound text is 
not shown, the header is "HTTP/1.1 200 Ok" and the Group Footer includes 
a pagelist with backlinks.

This can be overridden in local configuration, for example:

   # Show PageNotFound for category pages that don't exist
   if (preg_match("/^Category\\./", $pagename)) {
     $DefaultPageTextFmt = '(:include Site.PageNotFound:)';
     $PageNotFoundHeaderFmt = 'HTTP/1.1 404 Not Found');
   }

> Is it possible to test, in code, if a category exists?
> (I want to count in TotalCounter hits on Category pages for categories
> that do exist only, as TotalCounter (no longer) counts (the very many)
> hits to pages that do not exist).

It depends on what does "category exists" means. If it is "Category page 
exists", you have the PageExist($pagename) function.

Look up the documentation about $AutoCreate on how to automatically 
create category pages when saving a page linking to them.

OTOH if "category exists" means "there are currently incoming links", 
you can check if a pagelist has any pages, then the category "exists".

   # if you call your code before stdconfig.php
   include_once("$FarmD/scripts/pagelist.php");

   # define array and options
   $list = [];
   $opt = [ 'link' => $pagename ];
   FPLTemplatePageList($pagename, $list, $opt);

   # $list has now pages that link to $pagename.
   if($list) {} # 1+ incoming links, category "exists"


> Is it possible to have PmWiki not render a category page if the
> category does not exist?

To display the Site.PageNotFound text when there are no incoming links, 
you can place in the pagelist "template none" section:

   (:include Site.PageNotFound:)

I would probably create a pagelist template for the Category listings 
separate from the search templage.

Petko