I’ve created a $contact_details array:

$json = file_get_contents('current.json');
$contacts = json_decode($json, true);
$contacts_data = [];

for ($i = 0; $i < count($contacts); $i++) {
    $contacts_data[$i]['email'] = $contacts[$i]['Email'];
    $contacts_data[$i]['fields'] = [
            "id" => 1,
            "value" => $contacts[$i]['Appointments Booked']
    ];
}

That outputs this:

Array
(
    [0] => Array
        (
            [email] => [email protected]
            [fields] => Array
                (
                    [id] => 1
                    [value] => 104
                )

        )

    [1] => Array
        (
            [email] => [email protected]
            [fields] => Array
                (
                    [id] => 1
                    [value] => 4
                )

        )
)

That I then pass into a request:

curl_setopt_array($curl, [
  CURLOPT_URL => "https://test.api-us1.com/api/3/import/bulk_import",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'callback' => [
        'requestType' => 'POST',
        'detailed_results' => 'true',
        'url' => 'test.com'
    ],
    'contacts' => $contacts_data
  ]),
  CURLOPT_HTTPHEADER => [
    "Api-Token: 1234567890",
    "Content-Type: application/json",
    "accept: application/json"
  ],
]);

However, the API responds with:

"failureReasons":
[{"contact":1,"failureReason":"Field 'fields.id' must be an integer"},
{"contact":2,"failureReason":"Field 'fields.id' must be an integer"}]}

I’m totally stumped. Based on the output of my $contact_details array, it appears that the “id” key has an integer value of 1 for both contacts.