Match values from two arrays to return posts. wp_query?

Just to make sure there are no spaces in the comma seperated list try changing this:

$array = explode(',', $list);

to this

$array = array_map( 'trim', (array)  explode(',', $list) );

I don’t think it’s possible with a (single) meta query. Let me know if this scenario is correct:

On a ‘stores’ single post page you’re querying for brands posts that have a ‘brand_name’ custom field value that’s in the ‘store_brands’ custom fields values. I assume the ‘brands_name_alt’ values are never the same as the ‘store_brands’ or ‘brand_name’ values?

I think you should first get all meta values for the ‘brands_name_alt’ key where posts have the ‘brand_name’ key in the ‘store_brands’ values. Then use the values in the WP_Query.

Try it with this:

global $wpdb;

$list = get_post_meta( $post->ID, "store_brands", true );
$array = array_filter( array_map( 'trim', (array)  explode( ',', $list ) ) );

if ( !empty( $array ) ) {

	$post_types = array( 'brands', 'stores' );

	$post_type_sql  = "'" . implode( "', '", array_map( 'esc_sql', $post_types ) ) . "'";
	$meta_value_sql = "'" . implode( "', '", array_map( 'esc_sql', $array ) ) . "'";

	// Firs query to get the brands_name_alt meta values
	$query = "SELECT $wpdb->postmeta.meta_value FROM $wpdb->posts
          INNER JOIN $wpdb->postmeta ON ( $wpdb->posts.ID = $wpdb->postmeta.post_id )
          INNER JOIN $wpdb->postmeta AS mt1 ON ( $wpdb->posts.ID = mt1.post_id )
          WHERE $wpdb->posts.post_type IN ( $post_type_sql )
          AND $wpdb->posts.post_status = 'publish'
          AND (
          	   $wpdb->postmeta.meta_key = 'brands_name_alt'
	           AND mt1.meta_key = 'brand_name'
	           AND CAST( mt1.meta_value AS CHAR) IN ( $meta_value_sql )
              )
          GROUP BY wp_posts.ID
          ORDER BY wp_posts.post_date DESC";

	$meta_values = $wpdb->get_col(  $query );

	$args = array(
		'post_type' => $post_types,
		'meta_query' => array(
			'relation' => 'OR',
			array(
				'key'     => 'brand_name',
				'value'   => $array,
				'compare' => 'IN'
			),
		),
	);

	// Check if meta values were found for the brands_name_alt key
	if ( !empty( $meta_values ) ) {

		// merge all meta values
		$all_values = array();
		foreach ( $meta_values as $value ) {
			$value = array_filter( array_map( 'trim', (array)  explode( ',', $value ) ) );
			$all_values = array_merge( $all_values, $value );
		}

		// get all brands_name_alt posts
		$args['meta_query'][] =  array(
			'key'     => 'brands_name_alt',
			'value'   => $all_values,
			'compare' => 'IN'
		);

		// get all store_brands posts
		$args['meta_query'][] =  array(
			'key'     => 'store_brands',
			'value'   => $all_values,
			'compare' => 'IN'
		);
	}

	$custom_query = new WP_Query( $args );

	// The rest of your loop
}

btw:
consider creating a child theme instead of editing your theme directly – if you upgrade the theme all your modifications will be lost.

When merging the $all_values array it creates a [value] array like this:

// part of the $args array
[2] => Array
                (
                    [key] => store_brands
                    [value] => Array
                        (
                            [0] => FordCar
                            [1] => Fored
                        )

                    [compare] => IN
                )

As you see this can be used by the meta_query.

That’s probably because you want it to return posts from the ‘store_brands’ posts which has no brand_name_alt key values.

But this should work.

$list = get_post_meta( $post->ID, "store_brands", true );
$array = array_filter( array_map( 'trim', (array)  explode( ',', $list ) ) );

$args = array(
    'post_type' => array('stores', 'brands'),
    'meta_query' => array(
        'relation' => 'OR',
        array(
            'key'     => 'brand_name',
            'value'   => $array,
            'compare' => 'IN'
        ),
        array(
            'key'     => 'store_brands',
            // just hardcoding the values
            'value'   => array('FordCar', 'Fored'),
            'compare' => 'IN'
        ),
    ),
);

$custom_query = new WP_Query($args);

It should return ‘brands’ post type posts with the brand name ‘Ford’ and posts with the store_brands key values FordCar or Fored.

Aha, It will indeed not work. as the value for ‘store_brands’ is a comma seperated string.

The only way this will work is if you add multiple ‘store_brand’ custom field values instead of the comma seperated ‘store_brand’ value.

This in your theme’s functions.php will add the individual custom fields everytime you update the comma seperated custom field ‘store_brands’.
You will not see these individual custom fields (in the edit post screen) because of the starting underscore in the custom field key name ‘_store_brands’.

add_action ( 'update_postmeta', 'update_hidden_store_brands_meta', 10, 4  );

function update_hidden_store_brands_meta( $meta_id, $object_id, $meta_key, $meta_value ) {

	$post = get_post( $object_id );

	if ( !$post ) {
		return;
	}

	if ( ( 'store_brands' === $meta_key ) && ( 'stores' === $post->post_type ) ) {

		delete_post_meta( $object_id, '_store_brands' );
		$meta_value = array_filter( array_map( 'trim', (array)  explode( ',', $meta_value ) ) );

		if ( !empty( $meta_value ) ) {
			foreach ( $meta_value as $value ) {
				add_post_meta( $object_id, '_store_brands', $value, false );
			}

		}
	}
}

You still have to update a post or the custom field ‘store_brands’ for the individual _store_brands fields to be added to a post.

Now use this code for the query:

global $wpdb;

$post_id    = absint( $post->ID );
$post_types = array( 'brands', 'stores' );
$list       = (array) get_post_meta( $post_id, "_store_brands", true );
$array      = array_filter( array_map( 'trim', $list ) );

if ( !empty( $array ) &&  $post_id ) {

	$post_type_sql  = "'" . implode( "', '", array_map( 'esc_sql', $post_types ) ) . "'";
	$meta_value_sql = "'" . implode( "', '", array_map( 'esc_sql', $array ) ) . "'";

	// First query to get the brands_name_alt meta values
	$query = "SELECT $wpdb->postmeta.meta_value FROM $wpdb->posts
          INNER JOIN $wpdb->postmeta ON ( $wpdb->posts.ID = $wpdb->postmeta.post_id )
          INNER JOIN $wpdb->postmeta AS mt1 ON ( $wpdb->posts.ID = mt1.post_id )
          WHERE $wpdb->posts.post_type IN ( $post_type_sql )
          AND $wpdb->posts.post_status = 'publish'
          AND $wpdb->posts.ID NOT IN ( $post_id )
          AND (
          	   $wpdb->postmeta.meta_key = 'brands_name_alt'
	           AND mt1.meta_key = 'brand_name'
	           AND CAST( mt1.meta_value AS CHAR) IN ( $meta_value_sql )
              )
          GROUP BY wp_posts.ID
          ORDER BY wp_posts.post_date DESC";

	$meta_values = $wpdb->get_col(  $query );

	$args = array(
		'post_type'    => $post_types,
		'meta_query'   => array(

			'relation' => 'OR',

			array(

				// Nested queries are allowed since WordPress 4.1
				'relation' => 'OR',

				array(
					'key'     => 'brand_name',
					'value'   => $array,
					'compare' => 'IN'
				),

				array(
					'key'     => '_store_brands',
					'value'   => $array,
					'compare' => 'IN'
				),
			)
		),
	);

	// Check if meta values were found for the brands_name_alt key
	if ( !empty( $meta_values ) ) {

		// merge all meta values
		$all_values = array();
		foreach ( $meta_values as $value ) {
			$value = array_filter( array_map( 'trim', (array)  explode( ',', $value ) ) );
			$all_values = array_merge( $all_values, $value );
		}

		// Query for all posts with the store_brands values in the brands_name_alt values
		$args['meta_query'][] =  array(
			'key'     => '_store_brands',
			'value'   => $all_values,
			'compare' => 'IN'
		);
	}

	$custom_query = new WP_Query( $args );

	// The rest of your loop
}

However I think this will return stores? rather than brands?

Did you test it after updating some posts with the (comma seperated) ‘store_brands’ custom field?

In my test site it returns brands and stores posts.

1 brand_name CF values posts that are in the _store_brands CF values of the current post
2 _store_brands CF values posts that are in the _store_brands CF values of the current post
3 _store_brands CF values posts that have _store_brands CF values in the brands_name_alt CF values (from the posts in #1)

It’s getting increasingly more difficult to describe 🙂