用PHP解析json(parse json with php)

 我是一个php newb，并且在理解如何解析json api返回时遇到一些问题。 这是json的片段： 
 
{
  "results": [
    {
     "list_name": "",
     "display_name": "",
     "updated": "",
     "bestsellers_date": "",
     "published_date": "",
     "isbns": [
      {
       "isbn10": "",
       "isbn13": ""
      },
      {
       "isbn10": "",
       "isbn13": ""
      }
    ],
    "book_details": [
     {
      "title": "Book author",
      "description": "Book description"",
      "contributor": "",
      "author": "Book author",
      "contributor_note": "",
      "price": ,
      "age_group": "",
      "publisher": "",
      "primary_isbn13": "1010101010",
      "primary_isbn10": "1010101010101"
     }
   ],
    "reviews": [
      {
       "book_review_link": "",
       "first_chapter_link": "",
       "sunday_review_link": "",
       "article_chapter_link": ""
     }
   ]
 },
 
 这是我到目前为止的PHP ... 
 
<?php

$json=file_get_contents('the url for the api return');

// create array
$json_a=json_decode($json,true);

foreach($json_a[results] as $r)
{
echo '

List: '.$r[list_name].'
<br />
Title: '.$r[title].'
<br>
Description: '.$r[description].'
<br />
<br />
';
}

?>
 
 我从api返回，它为'list_name'提供了正确的值，但'title'和'description'仍未填充; 所以，我知道我没有正确访问这些子键（？）。 获取这些元素的正确语法是什么？ 
 
 真的很感谢你们所提供的任何指导。 提前致谢。 

I'm a php newb and having some problems understanding how to parse a json api return. Here is a snippet of the json:
 
{
  "results": [
    {
     "list_name": "",
     "display_name": "",
     "updated": "",
     "bestsellers_date": "",
     "published_date": "",
     "isbns": [
      {
       "isbn10": "",
       "isbn13": ""
      },
      {
       "isbn10": "",
       "isbn13": ""
      }
    ],
    "book_details": [
     {
      "title": "Book author",
      "description": "Book description"",
      "contributor": "",
      "author": "Book author",
      "contributor_note": "",
      "price": ,
      "age_group": "",
      "publisher": "",
      "primary_isbn13": "1010101010",
      "primary_isbn10": "1010101010101"
     }
   ],
    "reviews": [
      {
       "book_review_link": "",
       "first_chapter_link": "",
       "sunday_review_link": "",
       "article_chapter_link": ""
     }
   ]
 },
 
And here's the php I have so far...
 
<?php

$json=file_get_contents('the url for the api return');

// create array
$json_a=json_decode($json,true);

foreach($json_a[results] as $r)
{
echo '

List: '.$r[list_name].'
<br />
Title: '.$r[title].'
<br>
Description: '.$r[description].'
<br />
<br />
';
}

?>
 
I'm getting a return from the api and it's providing the correct value for 'list_name', but 'title' and 'description' remain unpopulated; so, I know I'm not accessing those subkeys(?) correctly. What is the correct syntax for getting at those elements?
 
Really appreciate any guidance y'all can provide on this. Thanks in advance.

原文：https://stackoverflow.com/questions/7355633