You can use insert_user_meta($user_id,'meta_key','meta_value');
when you want to get that keys, you can get like $keys = get_user_meta($user_id,'meta_key');
in $keys
variable you get an array of all keys.
You can use insert_user_meta($user_id,'meta_key','meta_value');
when you want to get that keys, you can get like $keys = get_user_meta($user_id,'meta_key');
in $keys
variable you get an array of all keys.