php - 从密钥名称获取JSON值

Question

I have a JSON similar to the following:

{
    "name": "Activities",
    "description": "Activities",
    "parent_group_id": 0,
    "display": "Activities",
    "group_id": 7,
    "stamps": [
        {
            "stamp_id": 14,
            "name": "Stamp 14",
            "rank": 2
        },
        {
            "stamp_id": 20,
            "name": "Stamp 20",
            "rank": 4
        }
    ]
},
{
    "name": "Games",
    "description": "Games",
    "parent_group_id": 0,
    "display": "Games",
    "group_id": 6,
    "stamps": [
        {
            "stamp_id": 33,
            "name": "Stamp 33",
            "rank": 3
        },
        {
            "stamp_id": 31,
            "name": "Stamp 31",
            "rank": 1
        }
    ]
}

I want to get a list of each of the stamp_ids seperated by commas through PHP (eg. 14,20,33,31)

I have already tried this, with no luck:

$stampsdata     = json_decode($stampsjson, true);
$numberofstamps = $stampsdata['stamps']['stamp_id']);

Can anyone help?

Answer 1

decode the JSON with json_decode and use array_column to get the IDs.

working solution:

// true needed to transform object to associative array
// $json contains your JSON string

$data = json_decode($json, true);

$stamps = [];
foreach ($data as $obj) {
    $stamps[] = array_column($obj['stamps'], 'stamp_id');
}

// implode sub arrays and concatenate string
$str = '';

foreach ($stamps as $stamp) {
    $sub = implode(',', $stamp);
    $str .= $sub . ',';
}

// remove trailing comma
$stampIds = rtrim($str, ',');
print ($stampIds);