Using a Shortcode to List Posts from Multiple Categories

Question

I have a shortcode that takes 1 argument for post category slug and returns and list of posts.

    //[list-products] creates the product table in the wholesale page, can be used to create a table list of any category

function list_products_func ( $atts ) {

$a = shortcode_atts( array (
  'category' => '',
), $atts);

  $args = array(
      'posts_per_page' => -1,
      'tax_query' => array(
          'relation' => 'AND',
          array(
              'taxonomy' => 'product_cat',
              'field' => 'slug',
              'terms' => $a['category']
          )
      ),
      'post_type' => 'product',
      'orderby' => 'title,'
  );

  $products = new WP_Query( $args );
  echo "<table>";
  while ( $products->have_posts() ) {
      $products->the_post();
    $product = new WC_Product(get_the_ID());
      ?>
          <tr class="product-list-item">
              <td><a href="<?php the_permalink(); ?>">
                  <?php the_title(); ?>
              </a></td>
              <td>
                  <?php echo get_the_excerpt(); ?>
              </td>
              <td>
                  <?php echo $product->get_price_html(); ?>
              </td>
          <td>
          <?php echo woocommerce_quantity_input(
            array(
                'min_value' => 1,
                'max_value' => $product->backorders_allowed() ? '' : $product->get_stock_quantity(),
            )); ?>
          </td>
          <td>
          <?php echo woocommerce_template_loop_add_to_cart(); ?>
          </td>
          </tr>
      <?php
  }
  echo "</table>";
}
add_shortcode ( 'list_products' , 'list_products_func' );

I'd like it to be able to take any number of categories and return the posts that match BOTH categories. In this use case, it is being used by a coffee distributor to show WooCommerce products that have a category of wholesale and one of their coffee subcategories distinct-well-defined or whatever.

The way it is used is [list-products CAT1 CAT2]

I tried just typing the shortcode with commas and hoping the code interpreted that correctly, but that didn't work.

Any help would be appreciated.

Update

It turns out I actually need it to filter products so it only shows products that have both categories, not showing all products in both categories.

Answer 1

Maybe you can make it so that you can use the shortcode like [list-products categories="1,2,3"], and then explode them as an array to insert them as your terms?

<?php
function list_products_func($atts) {

   $a = shortcode_atts(array(
      'categories' => '',
   ), $atts);

   // Check for multiple categories by comma
   if ( strpos( $a['categories'], ',' ) !== false ) {
      $terms = explode( $a['categories'] );
   } else {
      $terms = $a['categories'];
   }

   $args = array(
      'posts_per_page'  => -1,
      'tax_query'       => array(
         'relation'     => 'AND',
         array(
            'taxonomy'  => 'product_cat',
            'field'     => 'slug',
            'terms'     => $terms // Your exploded terms array 
         )
      ),
      'post_type' => 'product',
      'orderby'   => 'title,'
   );

   $products = new WP_Query($args);
   echo "<table>";
   while ($products->have_posts()) {

      $products->the_post();
      $product = new WC_Product(get_the_ID()); ?>
      <tr class="product-list-item">
         <td><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></td>
         <td><?php echo get_the_excerpt(); ?></td>
         <td><?php echo $product->get_price_html(); ?></td>
         <td>
            <?php echo woocommerce_quantity_input(
            array(
               'min_value' => 1,
               'max_value' => $product->backorders_allowed() ? '' : $product->get_stock_quantity(),
            )); ?>
         </td>
         <td><?php echo woocommerce_template_loop_add_to_cart(); ?></td>
      </tr>
      <?php

   }
   echo "</table>";
}
add_shortcode('list_products', 'list_products_func');
?>

Answer 2

This is an answer to the second part of my question, which I didn't realize until after the accepted answer came in.

First, I added the accepted answer from Robbert and this little for loop to expand the tax_query arguments dynamically:

//Generates an array of tax_query arguments
  $query_args = array ();
  foreach ( $terms as $term ) {
    array_push( $query_args, array (
          'taxonomy' => 'product_cat',
              'field' => 'slug',
              'terms' => $term
          )
    );
  }

  $args = array(
      'posts_per_page' => -1,
      'tax_query' => array(
          'relation' => 'AND',
          $query_args
      ),
      'post_type' => 'product',
      'orderby' => 'title,'
  );