Rewrite rule taxonomy url with different values in one function

You can do that using a subpattern or capturing group like ([a-z]) in your rewrite rule’s regex (i.e. regular expression pattern, which is the 1st parameter for add_rewrite_rule()), and then use $matches[<n>] in your query (the 2nd parameter for add_rewrite_rule()), where <n> is a number (1 or above) and it’s the subpattern’s position number.

Why use $matches: Because when matching the current URL against the rewrite rules on your site (i.e. rules which use index.php), WordPress will use preg_match() with the 3rd parameter set to $matches.

So for example in your case, you can try this which should match movies/a, movies/b, movies/c and so on, and that the $matches[1] would be the alphabet after the slash (e.g. c as in movies/c):

add_rewrite_rule(
    '^movies/([a-z])/?$',
    'index.php?taxonomy=movies_alphabet&term=$matches[1]',
    'top'
);

Notes:

I added $ to the regex, so that it only matches movies/<alphabet> like movies/a and not just anything that starts with that alphabet or path (e.g. movies/aquaman and movies/ant-man).
See this for more details on regex meta-characters like that $.
You can play with the above regex here. _{( PS: You can learn regex via this site; just check the explanation for the specific regex pattern.. 🙂 )}

Don’t forget to flush the rewrite rules — just visit the Permalink Settings admin page, without having to do anything else.

Bonus 😉

To support for pagination, e.g. the 2nd page at https://example.com/movies/a/page/2/, you can use the following regex and query:

Note that we now have 2 capturing groups — ([a-z]) and (\d+) (the page number). $matches[2] is used to get the page number and will be the value of the query var named paged.

add_rewrite_rule(
    '^movies/([a-z])(?:/page/(\d+)|)/?$',
    'index.php?taxonomy=movies_alphabet&term=$matches[1]&paged=$matches[2]',
    'top'
);

You can test the regex here, and once again, remember to flush the rewrite rules after making changes to your regex and/or query.

Happy coding!

Bonus 😉

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