PHP rewriting a json array (Undefined offset)

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.

What is contained in $array? var_dump($array). In your code above, you populate $json, not $array. — Michael Berkowski
– Michael Berkowski, Commented Jul 15, 2012 at 14:11
The array is probably indexed by string keys, not integers. also, where does $array show up? — Novak
– Novak, Commented Jul 15, 2012 at 14:12
@GuyDavid Or if its origin is JSON, they may be object properties. — Michael Berkowski
– Michael Berkowski, Commented Jul 15, 2012 at 14:13
@Michael I know my Valuable names might not be the same, that's because they are in different functions. $json is $array. — Throdne
– Throdne, Commented Jul 15, 2012 at 14:13
@Throdne very well then, please var_dump($json) or var_dump($array) so we can see what's in it! — Michael Berkowski
– Michael Berkowski, Commented Jul 15, 2012 at 14:13

Michael Berkowski · Accepted Answer · 2012-07-15 14:23:08Z

2

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];

edited Jul 15, 2012 at 14:23

answered Jul 15, 2012 at 14:17

Michael Berkowski

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3 Comments

Throdne Over a year ago

I see, But the problem is anytime $barcode changes, the ['ISBN:9781599953540'] will change also. I need to make my code dynamic. Is there anyway of doing it with array_keys(). Sorry, very new to PHP. Still learning.

Michael Berkowski Over a year ago

@Throdne do you only expect one item back each time, or many?

Michael Berkowski Over a year ago

@Throdne see addition above for array_keys() usage here.

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