使用PHP和laravel框架将对象数组存储在MySql数据库中

我正在使用PHP和laravel框架创建一个web应用程序。我的代码中有以下类。

class ReportField extends Model
{
    //
    public $name;
    public $quantity;
    public $unitCost;
    public $totalCost;
    public $estimation;
}

我使用序列化将这些对象的数组写入数据库。

$fieldsList=array();
foreach($items as $item){
        if($item->sale_type == 1){
                $reportField=new ReportField();
                $reportField->name=$item->item_name;
                $reportField->unitCost=$item->unit_cost;
                array_push($fieldsList,serialize($reportField));
         }
}
$gpForecast=new GPForecast();
$gpForecast->project_id=$project_id;
$gpForecast->fieldList=(serialize($fieldsList));
$gpForecast->save();

现在取消序列化后，我想将数组中的那些对象转换回RecordField对象。

$gpForecast=GPForecast::all()->first(); //here i read one of array i write to database
$fieldList=unserialize($gpForecast->fieldList );
foreach($fieldList as $field){
       echo $field->name;
}

但后来我得到了错误Trying to get property of non-object，那么我该如何更正呢？