WP_Query meta compare must include ALL array values

Question

I am allowing users to query posts using a form with checkboxes. I want the posts to be filtered by the checkboxes but instead of showing all posts that include the ANY of the meta values selected I want to show posts that contain all of the selected values. Is this possible? Here is what I currently have using the "IN" operator which just checks if the post contains any single value in the array.

$the_query = new WP_Query(array(
            'post_type' => 'listing',
            'posts_per_page' => -1,
            'post_status' => 'publish', 
            'category_name' => 'private_rental',
            'orderby' => 'rand',
            'meta_query' => array(
                    'key' => 'row_amenities',
                    'value' => $amenities,
                    'compare' => 'IN'
                    )
        ));

Answer 1

You can have multiple meta_query arguments with the same key and that will produce the results you're seeking. Here's an example:

$meta_query = array_map( create_function( '$a', 'return array("key" => "row_amenities", "value" => $a);' ), $amenities );

$the_query = new WP_Query(array(
            'post_type' => 'listing',
            'posts_per_page' => -1,
            'post_status' => 'publish', 
            'category_name' => 'private_rental',
            'orderby' => 'rand',
            'meta_query' => $meta_query
        ));

If $amenities will have a lot of values (> 10), you should probably take a different approach, because it will join the postmeta table for each meta_query.