get included reply in a recursive relationship in laravel 5

Did you add the relation? And if you did so, how did you create the relation? It seems like the relation doesn't exists on the Topic model

I write included_reply in Reply method only and call it via replies.included_reply. I did not write Topic Model here Because I thought it does not require.

if a relationship except included_reply is required ,What is it?

Can you show what you have now? This is really vague..

This is Topic Model :

<?php

    namespace App;

    use Cviebrock\EloquentSluggable\SluggableInterface;
    use Cviebrock\EloquentSluggable\SluggableTrait;
    use Illuminate\Database\Eloquent\Model;

    class Topic extends Model implements SluggableInterface
    {
        use SluggableTrait;

        protected $sluggable = [
            'build_from' => 'topic_subject',
            'save_to'    => 'topic_alias',
            'on_update'  => true
        ];

        protected $guarded    = ['created_at', 'updated_at'];
        protected $primaryKey = 'topic_id';
        protected $dateFormat = 'U';

        public function getCreatedAtAttribute ($value)
        {
            return $value;
        }
        
        public function replies (){
         return $this->hasMany('App\Reply');
        }
        public function user (){
            return $this->belongsTo('App\User','topic_by','user_id');
        }

    }

And this is Reply Model :

<?php

    namespace App;

    use Illuminate\Database\Eloquent\Model;

    class Reply extends Model
    {
        protected $guarded    = ['created_at', 'updated_at'];
        protected $primaryKey = 'reply_id';
        protected $dateFormat = 'U';

        public function getCreatedAtAttribute ($value)
        {
            return $value;
        }

        public function included_reply ()
        {
            return $this->with(['replies'=> function ($query) {
                return $query->where('reply_id',$this->embed_reply);
            }])->get();
        }

        public function topics ()
        {
            return $this->belongsTo('App\Topic');
        }

        public function user ()
        {
            return $this->belongsTo('App\User', 'reply_by', 'user_id');
        }

        public function files ()
        {
            return $this->hasMany('App\Userfile');
        }


    }

And this is show method on Topic Controller:

public function show ($alias)
        {
            $topic = Topic::whereTopicAlias($alias)
                ->with([
                    'replies' => function ($query) {
                        $query->orderBy('created_at', 'desc');
                    }
                    , 'replies.included_reply'
                ])
                ->first();
//          return $topic;
            return view('main.pages.forum.topic', ['topic' => $topic]);
        }

Reply Table :

    reply_id
    content
    topic_id
    reply_by
    embed_reply
    created_at
    updated_at

Topic Table :

    topic_id
    topic_subject
    topic_alias
    topic_by
    views_count
    replies_count
    created_at
    updated_at

These are all things that I have

There must be a relationship between your parent reply and your child reply :

public function embed()
{
    return $this->belongsTo(Reply::class, 'embed_reply');
}

$reply = Reply::find($reply_id);
$embed = $reply->embed;