Question

I have a PHP array that has numeric keys as a string type.

But when I try and access them PHP is giving me an undefined index error.

$a = (array)json_decode('{"1":1,"2":2}');
var_dump($a);
var_dump(isset($a[1]));
var_dump(isset($a["1"]));
var_dump($a[1]);
var_dump($a["1"]);

Output:

array (size=2)
    '1' => int 1
    '2' => int 2

boolean false

boolean false

ERROR: E_NOTICE: Undefined offset: 1

null

ERROR: E_NOTICE: Undefined offset: 1

null

How do I access these values?

Demo: http://codepad.viper-7.com/8O03IM

Answer 1

So, I haven’t seen any other answers touch upon this, but @xdazz came close.

Let’s start our environment, $obj equals the object notation of a decoded string:

php > $obj = json_decode('{"1":1,"2":2}');

php > print_r($obj);
stdClass Object
(
    [1] => 1
    [2] => 2
)

php > var_dump( $obj );
object(stdClass)#1 (2) {
  ["1"]=>
  int(1)
  ["2"]=>
  int(2)
}

If you want to access the strings, we know the following will fail:

php > echo $obj->1;

Parse error: parse error, expecting `T_STRING' or `T_VARIABLE' or `'{'' or `'$'' in php shell code on line 1

Accessing the object variables

You can access it like so:

php > echo $obj->{1};
1

Which is the same as saying:

php > echo $obj->{'1'};
1

Accessing the array variables

The issue with arrays is that the following return blank, which is the issue with typecasting.

php > echo $obj[1];
php >

If you typecast it back, the object is once again accessible:

php > $obj = (object) $obj;
php > echo $obj->{1};
1

Here is a function which will automate the above for you:

function array_key($array, $key){
    $obj = (object) $array;
    return $obj->{$key};
}

Example usage:

php > $obj = (array) $obj;
php > echo array_key($obj, 1);
1

php > echo array_key($obj, 2);
2