baoshi-was/app/UserWorkGroup.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class UserWorkGroup extends Model
{
    protected $table="user_workgroups";
    protected $fillable=['name'];

    public function users(){
        return $this->belongsToMany('App\User','user_workgroup_user','user_workgroup_id','user_id');
    }
}