WordPress search filter by custom field

Question

Does anyone know how to alter WordPress search to filter by query vars? The query vars are custom fields. For example, I have a custom post type "books" and I want users to be able to search based on the "book_author" custom field.

The url after I hit the search button looks like this:

?search_filter=book_author&s=tolkien&post_type=book

Any help would be greatly appreciated.

Answer 1

You will want to do something like this within your PHP code on a search page.

$args = array(
              'post_type' => 'book',
              'order' => 'asc',
              'meta_query' => array(
                  array(
                      'key' => $_GET['search_filter'],
                      'value' => $_GET['s'],
                      'compare' => 'IN',
                      )
                  )
              );
$loop = new WP_Query( $args );

of course you may want to look at securing the code against SQL injection etc etc but this gives you a starting point into creating a page which will do what you want.

I would recommend reading more about WP_Query, especially the parts about order by and parameters.