PHP json_decode depth parameter doesn't work

Question

PHP's json_decode function has a "depth" parameter, where you can specify how deep it will recurse. But the following code:

test = array(
    'name' => 'sean',
    'dob' => '12-20',
    'parents' => array(
        'father' => 'tommy',
        'mother' => 'darcy'
    )
);

foreach(range(1, 3) as $depth) {
    echo "-----------------\n depth: $depth\n";
    print_r(json_decode(json_encode($test), true, $depth));
}

Produces this output:

-----------------
 depth: 1
-----------------
 depth: 2
-----------------
 depth: 3
Array
(
    [name] => sean
    [dob] => 12-20
    [parents] => Array
        (
            [father] => tommy
            [mother] => darcy
        )

)

What I would expect is a depth of 1 to show "name" and "dob", and a depth of 2 to show the parents, also. I don't get why a depth of 1 or 2 displays nothing at all.

Can anyone explain to me what I'm not understanding?

Answer 1

The documentation says why.

NULL is returned if the json cannot be decoded or if the encoded data is deeper than the recursion limit.

Answer 2

the problem here is that you didn't understand the depth parameter correctly

the depth of your test array is 3 and so it will not be printed in the first two iterations and a null value is returned

but in the 3rd iteration it gets printed because its depth is equal to the $depth [i.e. 3]