why same category base and single post base don't work?

Question

I have checked a similar question on the site but there was no satisfactory answer? Here is what I would like to accomplish.

When I set the permalink structure to '/blog/%postname%/' this gives me the result I want.

mydomain.com/blog/my-post

However, when I also add category base 'blog' it creates an error.

This is what I would want to get:

'mydomain.com/blog/my-category'

I know this has got something to do with wp_query and how wordpress resolves permalinks but, can someone explain why it fails? I mean the logic?

I have seen some sort of tricks to overcome this but I want to stay within the natural functionality of wordpress and follow the best practices.

Any explanation is much appreciated. Thanks.

Answer 1

When you set WordPress up with:

The set-up

Custom Permalink Structure: /blog/%postname%/
Category base: blog

Generated rewrite rules

WordPress generates these rewrite rules:

1. blog/([^/]+)(?:/([0-9]+))?/?$ => index.php?name=$matches[1]&page=$matches[2]
2. blog/(.+?)/?$ => index.php?category_name=$matches[1]

Rewrite rule position in the rewrite_rules_array

Your post rewrite rule (#1) is positioned earlier (therefore higher priority) than the category rewrite rule (#2) in your rewrite_rules_array. This allows your post URLs to work and causes your category URLs to fail.

Where the rewrite rule is positioned in the rewrite_rules_array matters.

Similar regular expression pattern

The regular expression in your post rewrite rule (#1) matches both mydomain.com/blog/my-post and mydomain.com/blog/my-category. So, when you attempt to visit https://example.com/blog/<category_name>, WordPress does this:

Using this:

blog/([^/]+)(?:/([0-9]+))?/?$ => index.php?name=$matches[1]&page=$matches[2]

converts this:

https://example.com/blog/some-category

into this:

index.php?name=some-category&page=

(page is automatically added by WordPress for front-page pagination).

Since name is in the query string, WordPress searches for a post with post_name (slug) of some-category and tries to display it using a single post template (e.g. single.html). This likely results in a 404 (not found) page. The desired outcome is to have WordPress recognize some-category as a category_name and display the results using a category archive template (e.g. category.html).

Solution

Using a WP_Rewrite->front (blog) and a matching Category base (blog) violates conventional WordPress configuration. WordPress uses a different front for different items: category for category, tag for tag. Notice that WordPress does not use the front category for both category and tag. Also, keep in mind the list of WordPress Reserved Terms.

If you must adhere to this non-conventional set-up, you should be able to do it using the template_redirect action hook. The idea is to test is_404() to see if the situation presented under Similar regular expression pattern has occurred. If it did, run a new WP_Query with arguments that look for results using the category_name parameter. The remainder of your solution is found in the answer to this question in WordPress Stack Exchange: Load a specific post if user tries to access 404 page. Be careful to set the appropriate conditional tag property (is_category) to true.