Adding Rewrite Rules In WordPress Tutorial

In this blog, we will learn about how to create rewrite rules in WordPress.

The problem

Let’s say we want to have a monthly archive page for a term. WordPress has a term archive page, which is /{taxonomy}/{term}/ , but does not have a monthly archive page for that term. This means /{taxonomy}/{term}/{year}/{month}/ does exist by default.

The solution

1. Add a rewrite rule:
   We can add a rewrite rule for the required URL structure.
   So when the user hits our required URL
   e.g. /movies/harry-potter/2021/11/ ,
   it will be interpreted as :
   index.php?archive_taxonomy=movies&archive_term=harry-potter&archive_year=2021&archive_month=11
2. Load our custom page template
   This custom template will have access to query params containing archive_taxonomy, archive_term, archive_year, archive_month

We add the rewrite rule so that we have a pretty URL, we don’t end up creating the ugly URL structure with query params.

How do we achieve this?

So let’s get started folks!

Step 1. Add rewrite rule

The add_rewrite_rule() function adds additional rules to the rewrite array. There are three arguments:

• rule — a regular expression with which to compare the request URL against
• rewrite — the query string used to interpret the rule. The $matches array contains the captured matches and starts from index '1'.
• position — ‘top' or 'bottom'. Where to place the rule: at the top of the rewrite array or the bottom. WordPress scans from the top of the array to the bottom and stops as soon as it finds a match. In order for your rules to take precedence over existing rules, you'll want to set this to 'top'. Default is 'bottom'.

add_action( 'init',  function() {
   /**
    * ([^/]*) - taxonomy
    * ([^/]*) - term
    * ([0-9]{4}) - year 2021
    * ([0-9]{2}) - month 11
    *
    */
   add_rewrite_rule(
      '([^/]*)/([^/]*)/([0-9]{4})/([0-9]{2})/?$',
        'index.php?archive_taxonomy=$matches[1]&archive_term=$matches[2]&archive_year=$matches[3]&archive_month=$matches[4]',
        'top'
    );
} );

So here,
There are four parts to this structure ’([^/]*)/([^/]*)/([0–9]{4})/([0–9]{2})/?$'

1. ([^/]*) will look for the regex match and replace the $matches[1] with the URL value and set that equal to archive_taxonomy query param. e.g. archive_taxonomy=movies
2. The next ([^/]*)will look for the regex match and replace the $matches[2] with the URL value and set that equal to archive_taxonomy query param. e.g. archive_term=harry-potter
3. ([0–9]{4})will look for the regex match and replace the $matches[3] with the URL value and set that equal to archive_year query param. e.g. archive_year=2021 . Notice {4} in the regex is because there are four numbers in the year pattern e.g.2021
4. The next ([0–9]{2})will look for the regex match and replace the $matches[2] with the URL value and set that equal to archive_month query param. e.g. archive_month=11 . Notice {2} in the regex is because there are four numbers in the month pattern e.g. 11

Step 2. Whitelist the query param

WordPress does not automatically recognize these query params, ( archive_taxonomy , archive_term ,archive_year and archive_month ) even though it's interpreted as a GET variable.

So we need to whitelist these like so :

add_filter( 'query_vars', function( $query_vars ) {
   $query_vars[] = 'archive_taxonomy';
   $query_vars[] = 'archive_term';
   $query_vars[] = 'archive_year';
   $query_vars[] = 'archive_month';
   return $query_vars;
} );

Step 3. Flush the previous rewrite rules.

Flush permalinks. Go to WP Admin > Settings > Permalinks > Save. This doesn’t happen automatically after you add the above code.

Step 4. Create Page Template.

Create a page template called taxonomy-date-archive.php . Here should to access the query param values, after step 5 is added.

<?php
/**
 * Template Name: Taxonomy Date Archive.
 *
 */

echo 'Hello World';

echo '<pre/>';
print_r(get_query_var( 'archive_taxonomy' ));
echo '<br>';
print_r(get_query_var( 'archive_term' ));
echo '<br>';
print_r(get_query_var( 'archive_year' ));
echo '<br>';
print_r(get_query_var( 'archive_month' ));

Step 5. Load the custom template for that rewrite URL.

Check if those query param exist, then load your custom page template else let the default template be loaded.

add_action( 'template_include', function( $template ) {
   if ( get_query_var( 'archive_taxonomy' ) == false || get_query_var( 'archive_taxonomy' ) == '' ) {
      return $template;
   }

   return get_template_directory() . '/taxonomy-date-archive.php';
} );

Output/Result

Now if we go to the URL /movies/harry-potter/2021/11/, our custom page template will load giving us access to all query params, using which we can run our query.

That’s all folks.