Meta query array - same order as specified order in value

Question

I have a custom Wordpress query that is using an array of product IDs that exist in an ACF field(these IDs do not line up with the Wordpress post IDs). I would like for the order of the returned posts to match the order of the array that is specified in the meta_query value. Here is what my meta query looks like:

$product_ids = array('3624', '1298', '430', '5629', '765');

$meta_query = array(
    'relation' => 'AND',
    array(
        'key' => 'product_id',
        'value' => $product_ids,
        'compare' => 'IN'
    ),
);

So, for instance, in the returned results I want the first product to be product ID 3624, and the last product to be 765. Is there a way to order the query results so that the order of the returned posts matches the order of the array specified in the meta query? I tried leaving orderby blank, but that seems to default to sorting by post ID. I also tried setting orderby to none, but that didn't seem to work either.

Answer 1

Use PHP to sort the results after the query (untested):

$product_ids = array( 3624, 1298, 430, 5629, 765 );

$query = new WP_Query( array(
    'meta_query' => array(
        'relation' => 'AND',
        array(
            'key'     => 'product_id',
            'value'   => $product_ids,
            'compare' => 'IN',
        ),
    ),
) );

$posts_by_product_id = array();
$sorted_posts = array();

if ( $query->have_posts() ) {
    foreach ( $query->posts as $post ) {
        $product_id = get_post_meta( $post->ID, 'product_id', true );
        $posts_by_product_id[ $product_id ] = $post;
    }

    foreach ( $product_ids as $product_id ) {
        if ( ! array_key_exists( $product_id, $posts_by_product_id ) ) {
            continue;
        }

        $sorted_posts[] = $posts_by_product_id[ $product_id ];
    }

    $query->posts = $sorted_posts;
}

The $query->posts property will contain the found posts, ordered by product ID to match the order in $product_ids.

Answer 2

If the post type is product, and $product_ids is a list of IDs of products that you want to retrieve, then you can do this rather simply (untested):

$product_ids = array( 3624, 1298, 430, 5629, 765 );

$query = new WP_Query( array(
   'post_type' => 'product',
   'post__in'  => $product_ids,
   'orderby'   => 'post__in',
) );