laravel 修改created_at默认存储方式

<?php
namespace Pcb\Model;
use  Illuminate\Database\Eloquent\Model  as Eloquent;

class PcbOrder extends Eloquent
{
    protected $connection="pcb";
    protected $table = 'order';
    protected $primaryKey = 'order_id';
    const CREATED_AT = 'create_time';
    const UPDATED_AT = 'update_time';
    public $timestamps = true;




    public function fromDateTime($value){
        return strtotime(parent::fromDateTime($value));
    }
    
    
    
    
    
    
}