I have a custom post type called "conference". I want to create a specific meta key for users who have registered for the conference. For example the meta key slug would be registered_users which stores an array with all ID's of registered users.
Is it possible ? How to create it ? And how to update it when a new user registers? I know how to update a basic meta, but here it's an array... :/
A postmeta value can be an array. You save it the exact same. Updating/Getting postmeta will detect if the value is an array/object, and serialize the value so it can be stored in the database.
// Saving
$users = array( 5, 20, 25, 29, 30 );
$saved = update_post_meta( get_the_ID(), 'registered_users', $users );
// Getting
$users = get_post_meta( get_the_ID(), 'registered_users', true );
// array( 5, 20, 25, 29, 30 )
