Code-Snippets-Functions/Execute a function on a child site/Relevanssi/indexing-image-captions-for-the-posts.txt

add_filter( 'relevanssi_content_to_index', 'rlv_add_attachment_excerpts', 10, 2 );
/**
 * Indexes attachment excerpts for the parent post.
 *
 * This function reads in the attachment excerpts from the database and
 * adds it to the parent post content.
 *
 * @global $wpdb The WordPress database interface.
 *
 * @param string $content The added content.
 * @param object $post    The indexed post object.
 *
 * @return string The added content.
 */
function rlv_add_attachment_excerpts( $content, $post ) {
    global $wpdb;
    $results = $wpdb->get_col(
        $wpdb->prepare(
            "SELECT post_excerpt FROM $wpdb->posts WHERE post_parent = %d",
            $post->ID
        )
    );
    foreach ( $results as $excerpt ) {
        $content .= " $excerpt";
    }
    return $content;
}