json_decode return null when a value is empty

Question

I came across this problem when trying to decode json into an array, for instance,

it works fine like this,

$year = 2012;
$month = 3;

$json = '{"year":'.$year.', "month":'.$month.'}';
$config = json_decode($json,true);

var_dump($config); // return array.

but if I set one of the variable to null, for instance,

$year = 2012;
$month = null;

$json = '{"year":'.$year.', "month":'.$month.'}';
$config = json_decode($json,true);

var_dump($config); // return null

I am after this result,

array
  'year' => int 2012
  'month' => null

How can I return such result then?

score 3 · Accepted Answer · answered Mar 28 '12 at 18:00

That's because when you do

$json = '{"year":'.$year.', "month":'.$month.'}';

results in:

{"year":2012, "month":}

Which in itself is not a valid json, thus you are getting NULL, if you can help it do

$month = "null"

I got the following code:

$year = 2012;
$month = "null";

$json = '{"year":'.$year.', "month":'.$month.'}';
echo $json . "\n";
$config = json_decode($json,true);
var_dump($config);

results:

{"year":2012, "month":null}
array(2) {
  ["year"]=>
  int(2012)
  ["month"]=>
  NULL
}

json_decode return null when a value is empty

1 Answers1