PHP rewriting a json array (Undefined offset) - php

Question

I'm taking some json, made by OpenLibrary.org, and remake a new array from the info.
Link to the OpenLibrary json
here is my PHP code to decode the json:
$barcode = "9781599953540";
function parseInfo($barcode) {
$url = "http://openlibrary.org/api/books?bibkeys=ISBN:" . $barcode . "&jscmd=data&format=json";
$contents = file_get_contents($url);
$json = json_decode($contents, true);
return $json;
}
the new array I'm trying to make looks something like this:
$newJsonArray = array($barcode, $isbn13, $isbn10, $openLibrary, $title, $subTitle, $publishData, $pagination, $author0, $author1, $author2, $author3, $imageLarge, $imageMedium, $imageSmall);
but when I try to get the ISBN_13 to save it to $isbn13, I get an error:
Notice: Undefined offset: 0 in ... on line 38
// Line 38
$isbn13 = $array[0]['identifiers']['isbn_13'];
And even if I try $array[1] ,[2], [3].... I get the same thing. What am I doning wrong here! O I know my Valuable names might not be the same, that's because they are in different functions.
Thanks for your help.

Answer 1

Your array is not indexed by integers, it is indexed by ISBN numbers:
Array
(
// This is the first level of array key!
[ISBN:9781599953540] => Array
(
[publishers] => Array
(
[0] => Array
(
[name] => Center Street
)
)
[pagination] => 376 p.
[subtitle] => the books of mortals
[title] => Forbidden
[url] => http://openlibrary.org/books/OL24997280M/Forbidden
[identifiers] => Array
(
[isbn_13] => Array
(
[0] => 9781599953540
)
[openlibrary] => Array
(
[0] => OL24997280M
)
So, you need to call it by the first ISBN, and the key isbn_13 is itself an array which you must access by element:
// Gets the first isbn_13 for this item:
$isbn13 = $array['ISBN:9781599953540']['identifiers']['isbn_13'][0];
Or if you need a loop over many of them:
foreach ($array as $isbn => $values) {
$current_isbn13 = $values['identifiers']['isbn_13'][0];
}
If you expect only one each time and must be able to get its key without knowing it ahead of time but don't want a loop, you can use array_keys():
// Get all ISBN keys:
$isbn_keys = array_keys($array);
// Pull the first one:
$your_item = $isbn_keys[0];
// And use it as your index to $array
$isbn13 = $array[$your_item]['identifiers']['isbn_13'][0];
If you have PHP 5.4, you can skip a step via array dereferencing!:
// PHP >= 5.4 only
$your_item = array_keys($array)[0];
$isbn13 = $array[$your_item]['identifiers']['isbn_13'][0];