Redirect old query string URLs to new add_rewrite_rule URL

Question

I have a custom page like this:

website.com/show/?id=9999&n=show-name

/show/ is a WordPress page with a postid of 540. I added a rewrite rule to convert the URL to:

website.com/show/9999/show-name/

Here's the code I'm using in my theme's functions.php for the rewrite:

add_action( 'init', 'init_custom_rewrite' );

function init_custom_rewrite() {
    add_rewrite_rule(        
        '^show/([^/]*)/([^/]*)/?',        
        'index.php?page_id=540&id=$matches[1]&n=$matches[2]',        
        'top' );
}

add_filter('query_vars', 'my_query_vars', 10, 1);

function my_query_vars($vars) {
    $vars[] = 'id';
    $vars[] = 'n';
    return $vars;
}

Now the URL website.com/show/9999/show-name/ works correctly.

However, now I need to make sure that if someone tries to access the page using the old URL:

website.com/show/?id=9999&n=show-name

... that they will be redirected to the new SEO friendly url:

website.com/show/9999/show-name

How do I setup that redirect?

Answer 1

I figured it out. I put these rewrite rules in .htaccess:

RewriteCond %{QUERY_STRING} ^id=([^/]*)&n=([^/]*)$ 
RewriteRule ^show/?$ /show\/%1\/%2\/? [R=301,L]