arnorhs arnorhs - 2 months ago 6
PHP Question

Weird behavior of matching array keys after json_decode()

I've got some very weird behavior in my PHP code. I don't know if this is actually a good SO question, since it almost looks like a bug in PHP. I had this problem in a project of mine and isolated the problem:

// json object that will be converted into an array
$json = '{"5":"88"}';
$jsonvar = (array) json_decode($json); // notice: Casting to an array
// Displaying the array:
var_dump($jsonvar);
// Testing if the key is there
var_dump(isset($jsonvar["5"]));
var_dump(isset($jsonvar[5]));


That code outputs the following:

array(1) {
["5"]=>
string(2) "88"
}
bool(false)
bool(false)


The big problem: Both of those tests should produce bool(true) - if you create the same array using regular php arrays, this is what you'll see:

// Let's create a similar PHP array in a regular manner:
$phparr = array("5" => "88");
// Displaying the array:
var_dump($phparr);
// Testing if the key is there
var_dump(isset($phparr["5"]));
var_dump(isset($phparr[5]));


The output of that:

array(1) {
[5]=>
string(2) "88"
}
bool(true)
bool(true)


So this doesn't really make sense. I've tested this on two different installations of PHP/apache.

You can copy-paste the code to a php file yourself to test it.

It must have something to do with the casting from an object to an array.

Answer

It can be further simplified to this problem

$o = new stdClass;
$o->{5} = 1; //or even $o->{'5'} = 1;
$a = (array) $o;
print_r($a); // Array([5] => 1)
var_dump(isset($a[5])); // false
var_dump(isset($a['5'])); // false

It seems that this only happens when the property name is one that php would normally consider a numeric key in an array.

Definitely unexpected behavior to me.


edit Same issue here Casting an Array with Numeric Keys as an Object


edit#2 documented behavior http://www.php.net/manual/en/language.types.array.php#language.types.array.casting