api-szy-demo/app/Models/Message.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Message extends Model
{
    protected $table='message';

    public function get_message_reply(){
        return $this->hasOne(Message::class,'pid');
    }

    public function get_user(){
        return $this->hasOne(User::class,'id','user_id');
    }
}