OK, so first of all you'll need to add your own WP_Schedule event:
add_action( 'wp', function () {
if (! wp_next_scheduled ( 'mark_posts_as_featured_event' )) {
wp_schedule_event(time(), 'daily', 'mark_posts_as_featured_event');
}
} );
function mark_posts_as_featured_event_callback() {
// if there are sticky posts in our CPT, unstick them
$sticked_post_ids = get_option( 'sticky_posts' );
if ( ! empty ) {
$old_featured_posts = get_posts( array(
'post_type' => '<MY_POST_TYPE>',
'fields' => 'ids',
'post__in' => $sticked_post_ids,
) );
foreach ( $old_featured_post_ids as $post_id ) {
unstick_post( $post_id );
}
}
// stick new posts
// get_random_posts
$new_featured_post_ids = get_posts( array(
'post_type' => '<MY_POST_TYPE>',
'posts_per_page' => 3,
'orderby' => 'rand',
'fields' => 'ids',
) );
foreach ( $new_featured_post_ids as $post_id ) {
stick_post( $post_id );
}
}
add_action( 'mark_posts_as_featured_event', 'mark_posts_as_featured_event_callback' );