Dual url structure for categorized content

[LostKobrakai]

Websites often provide content not only as on list of stuff, but with some sort of category. The most flexible way in ProcessWire to manage such a categorization are with PageFields. Form example with a structure like this.

- Magazine (magazine)
	- Articles
		- Article 1 (article)
		- Article 2
		- Article 3
		- …
	- Categories
		- Category 1 (category)
		- Category 2
		- …

Templatenames in parentheses
 
Now all articles have a url structure like: "…/magazine/articles/articlename/"
The categories are looking like: "…/magazine/categories/categoryname/"
 
But it can be useful to also provide the articles as part of the categories like this: "…/magazine/categories/categoryname/articlename/"
 
Because ProcessWire doesn't provide such functionality by default, we'll use urlSegments. These have to be enabled in the template-settings for the category template. This template therefore fulfills two different jobs. Displaying a list of containing articles, as well as rendering the articles which are linked by the list. 
 
A simple example of a existing category.php could be:

<?php // category.php

$articles = $pages->find("template=article, category=$page");

// This example uses a deligated template approach.
// Feel free to use your own way of templating,
// but this is also a simple way to explain this.
$content = renderArticleList($articles);

include("./_main.php"); 

Now we need to include the logic to seperate the default rendered article-list to the now added rendering of the called article.

<?php // category.php

// Throw a 404 Error if more than one segment is provided
if($input->urlSegment2) throw new Wire404Exception();

if($input->urlSegment1){ // Show the called article 

	// Sanitize the input for pageNames
	$name = $sanitizer->pageName($input->urlSegment1);

	// Search for the article with this name
	$article = $pages->get("template=article, name=$name");

	// Throw an 404 error if no article is found
	if(!$article->id) throw new Wire404Exception();

	// Explicitly set the original url of the article for the <link type="canonical" href=""> tag
	$article->canonical = $article->url;

	// Render the page, like if it was normally called. 
	// $page->url will not updated to the "categorized" url for the rendering-part
	// so you need to have that in mind if you provide some sort of breadcrumb
	echo $article->render();

}else{ // Show the list of articles of the current category

	$articles = $pages->find("template=article, category=$page");

	// The generateCategoryUrls() function is new, because
	// $page->url would provide the wrong urls.
	// Details are provided later
	$content = renderArticleList( generateCategoryUrls($articles, $page) );

	include("./_main.php"); 

}

Now if we call this "…/magazine/categories/categoryname/articlename/" we'll get the right article rendered out instead of the article-list. Now we need to talk about the article-list, which would - without changes - still render the "wrong" urls to all those articles.

Therefore I added the generateCategoryUrls() function. This function iterates over the pageArray and adds a second url to all those articles.

<?php // part of _func.php

function generateCategoryUrls($list, $category){
	foreach($list as $item){
		$item->categoryUrl = $category->url.$item->name."/";
	}
	return $list;
}

The last thing missing is the actual template which gets rendered by renderArticleList(). This would normally call for $article->url to get the url to the article. We want this to render our second url if we are on a category site. To let the template still be useable by non category sites, we just change the parts, where to url is used form the current $article->url to $article->get("categoryUrl|url"). Only if the additional urls are provided they get rendered or it falls back to the normal urls of the articles.

There we go, with such a setup all categorized articles are reachable via both urls. 

A small addition to explain the $article->canonical I used in the category.php. For SEO it's not good to provide the same content on multiple pages without explicitly declaring which of the duplicated ones should be the original / indexed one. By providing the following link tag we provide this declaration. The extra field I use isn't really necessary, because $page->url still is the standart ProcessWire url of the shown article. But I like this to be visibile in the code, that this is a dublicate. 

<link rel="canonical" href="<?php echo $page->get("canonical|url") ?>"/>

Hope you like the explanation. Feel free to give feedback on this.

Based on the example shown in the wiki: http://wiki.processwire.com/index.php/URL_Segments_in_category_tree_example

[bernhard]

nice!

also a good read: https://processwire.com/talk/topic/1799-routes-and-rewriting-urls