How does Wordpress handle URLs?

Question

I encountered this (to me) unfamilliar behavior in Wordpress.

Consider a random site using WordPress with a page called example with no content. This is just a page type post and not a category, tag or any sort of hierarchy. A 404 error is triggered if I append characters after the last "/":

http://example.com/example/abc

I expect that but if I only type numbers after the final "/" no 404 error is triggered. For example loading:

http://example.com/example/1123456

gets me to example page and the numbers are kept in the URL. The numbers have no special meaning in this case. There could be any nuber there, but I would expect it to trigger a 404 as it does on other sites.

Appending numbers to the URL on index or category pages still seems to trigger a 404, but not on posts and pages.

I am wondering wether this is an actual feature of WordPress and if so, then what is its purpose?

Answer 1

This is as designed. Wordpress matches URL's through the built-in rewrite module. You can read about it here. In addition, the source code to follow what is happening with this process is located in wp-content/class-wp-rewrite.php.

The specific line that provides the behavior you are seeing is below.

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

This code will match on page/post-name, and any following number (this supports pagination). However, it will not match on non-characters after the post name. What is interesting is that even if the post does not have the specified page, it will still accept as legit.