json_decode works for me on your data:

print_r(json_decode('{
       "data": [
          {
             "name": "Joe Bloggs",
             "id": "203403465"
          },
          {
             "name": "Fred Bloggs",
             "id": "254706567"
          },
          {
             "name": "Barny Rubble",
             "id": "453363843"
          },
          {
             "name": "Homer Simpson",
             "id": "263508546"
          }
       ]
    }
', true));

Output:

Array
(
    [data] => Array
        (
            [0] => Array
                (
                    [name] => Joe Bloggs
                    [id] => 203403465
                )

            [1] => Array
                (
                    [name] => Fred Bloggs
                    [id] => 254706567
                )

            [2] => Array
                (
                    [name] => Barny Rubble
                    [id] => 453363843
                )

            [3] => Array
                (
                    [name] => Homer Simpson
                    [id] => 263508546
                )

        )

)

Setting the second argument to true returns an associative array.

The second argument to json_decode forces the JSON to unserialize to an associative array if it is truthy (it is falsy by default).

That is, use json_decode($json, true)

I don't know if this is the right place here to discuss php's default parameters but if i like to change it i would do it like this:

function my_json_decode($json, $assoc=true, $depth=512, $options=0) {
    return json_decode($json, $assoc, $depth, $options);
} 

I hope i understood your question correctly. Please correct me if i don't. I am not shure if the majority of use-cases need the assoc-argument set to true. But I fear there will be a lot of trouble if they change it to true right now, because a lot of code needs to be rewritten.

As per the documentation, you need to specify true as the second argument if you want an associative array instead of an object from json_decode. This would be the code:

$result = json_decode($jsondata, true);

If you want integer keys instead of whatever the property names are:

$result = array_values(json_decode($jsondata, true));

However, with your current decode you just access it as an object:

print_r($obj->Result);

have you tried json_decode($test, true) ?