Help me with this query - showing all threads that the user is able to see

A user can only view and post on a thread that the user is a "recipient" of. I have explained it in more detailed down below.

My tables structure:

threads table: user_id, subject, recipients (contains serialized array of users)

messages table: thread_id, user_id, body

participants table: thread_id, user_id, read_at, deleted_at

So what I want is a way to show all threads that the user is a recipient of. And if they have deleted the thread (each time a thread is created, the participants table is populated by each recipient). For instance, if a thread has 3 recipients, 3 rows will be created in the participants table with their user ID. And there they have an option to delete the thread to not see it when they are viewing all threads that "belongs" to them.

I do not know how I can figure out a way to show threads to users who are the recipients of the threads. Please help me tackle this issue. Thanks!

I tried the following code but no luck.

    $threads = Thread::all();
    $participant = Participant::where(['user_id' => uid()])->get();
    foreach ($threads as $thread) {
       $recipients = unserialize($thread->recipients);
        if (in_array(uid(), $recipients) || $thread->user_id == uid()) {
           $messages = (object)Participant::where(['user_id' => uid(), 'thread_id' => $thread->id])->paginate(10);
        }
    }

Demo:

A thread has been created:

The recipients' user_id's are: 4, 7, 8.

threads table:

id  | user_id | subject | recipients
-------------------------------------------------------------------
1   |       1 | Hello   | a:1:{s:7:"user_id";a:3:{i:0;i:4;i:1;i:7;i:2;i:8;}}

messages table:

id  | user_id | thread_id | body
--------------------------------------------
1   |       1 |         1 | How you doing?

participants table:

id  | user_id | thread_id | read_at
--------------------------------------------
1   |       1 |         1 | 2016-04-13 00:03:23
--------------------------------------------
1   |       4 |         1 | NULL
--------------------------------------------
1   |       7 |         1 | NULL
--------------------------------------------
1   |       8 |         1 | NULL