To do this, you have to specify true as the second argument if you want an associative array instead of an object from json_decode.
For that use this code:
$result = json_decode($jsondata, true);
To have integer keys instead of whatever the property names are:
$result = array_values(json_decode($jsondata, true));
In your case just access it as an object:
print_r($obj->Result);
I hope this helps you.