Pretty links with add_rewrite_rule and add_query_var

Question

I am trying to pass a variable from the url into a wordpress post.

1) I added add_query_var into functions.php, to retrieve the query string from the url

add_filter( 'init', 'add_model_more_query_var' );
function add_model_more_query_var()
{
    global $wp;
    $wp->add_query_var( 'model_more' );
}

2) I can retrieved the variable in my post with:

get_query_var( 'model_more', 1 );

The url structure that I am using is:

domain.com/post-type/post-title/?model_more=5

https://www.domain.com/model/benz/?model_more=5

https://www.domain.com/model/audi/?model_more=4

https://www.domain.com/model/ford/?model_more=12

Now I am trying to make the urls pretty, and rewrite them from

https://www.domain.com/model/benz/?model_more=5

To

https://www.domain.com/model/benz/model_more/5/

This is where I am stuck.

I have the following rewrite rule, but I get a 404 when I try to access the pretty url:

add_action('init','add_model_more_rewrite_rule');
function add_model_more_rewrite_rule()
{
    add_rewrite_rule(
        '^model_more/(\d*)$',
        'index.php?model_more=$matches[1]',
        'top'
    );
}

Answer 1

There are a couple of issues with your regular expression:

^model_more/(\d*)$
^--- Says "match start of line"

In your URLs, the start of the line is actually /model/, so ^model_more will never match. Instead, try a regex like this:

^model/[^/]+/model_more/(\d+)/?$

• [^/]+ says "match anything except /, since I would guess there are multiple models under /model/.
• (\d+) ensures that only digits are captured - (\d*) would capture anything after the number.
• /?$ says "the end of the line might be preceded by a slash, but not necessarily.

Edit: You can see the regex in action at https://regex101.com/r/OhOFTD/1