Get a Submit Loop based mostly on Logged in Person info right into a Shortcode

I’ve a follower button on customers profiles the place customers can observe different customers. I’ve a web page template that reveals all posts by customers the at the moment logged in consumer follows. I wish to create a shortcode [following_loop] for this as an alternative and add the question to the capabilities.php. I am unable to get the shortcode to work.

Right here is the web page template that I used to be utilizing. How can I get this into the shortcode?

perform register_shortcodes(){
   add_shortcode('following_users', 'following_users_function');
}
add_action( 'init', 'register_shortcodes');
perform following_users_function () {

    $currentloggedinuser = get_current_user_id();

  // Get array containing solely the user_id1 values.

  $followers = $wpdb->get_col(
    $wpdb->put together(
      "SELECT user_id1 FROM {$wpdb->prefix}followers WHERE user_id2 = %d",
      $currentloggedinuser      
    )   
  );

  type($followers); // or apply sorting within the question above

  // Immediately echo the imploded array. 
  echo implode(', ', $followers);

  $args = array(
    'author__in'=> $followers, //use the array we received from the question
    'post_type' => 'submit'
  );
    
    if (have_posts()) :
      whereas (have_posts()) : the_post();
         $return_string = '<a href="'.get_permalink().'">'.get_the_title().'</a>';
      endwhile;
   endif;
    
    wp_reset_query();
   return $return_string;
}

Thanks prematurely 🙂