php - 注意：带有 while 循环的未定义索引

Question

我在 php 中收到以下错误：Notice: Undefined index: panel_num.

我想我需要使用isset()，但我似乎无法使用它while

global $d;
$i = 1;
while($i <= $d['panel_num']){
$options[] = array(
                      "name" => "Panel".$i,
                        "id" => "panel_".$i,
                       "std" => "",
                      "type" => "panel");
$i++;
}

解决此问题的正确方法是什么？

Answer 1

在使用它之前检查是否设置了该变量：

global $d;
if (isset($d['panel_num']))
{
  $i = 1;
  while($i <= $d['panel_num']){
  $options[] = array(
                      "name" => "Panel".$i,
                        "id" => "panel_".$i,
                       "std" => "",
                      "type" => "panel");
  $i++;
  }
}

Answer 2

我认为你只需要检查isset()而不是empty $d['panel_num']

global $d;
if(isset($d['panel_num']) && !empty($d['panel_num']))
{
    $i = 1;
    while($i <= $d['panel_num']){
    $options[] = array(
                  "name" => "Panel".$i,
                    "id" => "panel_".$i,
                   "std" => "",
                  "type" => "panel");
    $i++;
    }
}

因此，如果未设置或为空，您将避免调用您的变量