如何在json中获取字段名称

Question

我有json数据，就这样说吧

$string='[{"main_menu_id":"1","main_menu_caption":"Home","main_is_get_from_page":"0","is_sub_menu":"0","main_url_page":"","sub_menu_caption":"","caption_type":"","sub_is_get_from_page":"","sub_url_page":"","sub_additional_param":""}]';

如何仅在此json数据中获取字段名称？ 我期望的结果是main_menu_id，Main_menu_caption等。我需要提取keyname而不是值

Answer 1

$string='[{"main_menu_id":"1","main_menu_caption":"Home","main_is_get_from_page":"0","is_sub_menu":"0","main_url_page":"","sub_menu_caption":"","caption_type":"","sub_is_get_from_page":"","sub_url_page":"","sub_additional_param":""}]';
$arrJson  = array();
$arrJson  = json_decode($string);
foreach($arrJson as $key=>$value){
  foreach($value as $keyval=>$val){
    echo $keyval."<br>";
  }
}