Verified hash

Some endpoints require a hash query parameter that contains a hash verifying the POST request body data. The hash is comprised of the query parameters sorted by name, concatenated (recursively) into one string, hashed (sha256) with SHthe client signature secret and finally base64 URL encoded. The verification hash ensures that the data being POST-ed has not been tampered with by a middleman.

Note: After the string is base64 encoded you should replace + with - and / with _. Also you should remove trailing =.

The sort algorithm is natsort ("Natural order string comparison").

    "a" : "zebra",
    "x" : "banana",
    "c" : {
        "b" : "orange",
        "c" : "monkey",
        "a" : "sun"
    "b" : "tree"

Should give the following string after concat: zebratreesunorangemonkeybanana

Hashing example


function recursiveArrayToString($data)
    if (!is_array($data)) {
        return "$data";
    $ret = "";
    uksort($data, 'strnatcmp');
    foreach ($data as $v) {
        $ret .= recursiveArrayToString($v);
    return $ret;

function base64UrlEncode($input)
    return rtrim(strtr(base64_encode($input), '+/', '-_'), '=');

function createHash($data, $secret)
    $string = recursiveArrayToString($data);
    return base64UrlEncode(hash_hmac("sha256", $string, $secret, true));

$sign_secret = 'foobar';

$data = [
    'requestReference' => $ref, // unique to reqest
    'clientReference' => $localOrderId, // freely useable by client
    'paymentOptions' => 2,
    'items' => [
        ['productId' => 100002, 'clientItemReference' => 'first item'],
        ['name' => 'A magazine', 'description' => 'It is really great', 'price' => 2000, 'vat' => 2500],
        ['productId' => 100002, 'name' => 'Banana',  'description' => 'One', 'price' => 1500, 'vat' => 2500, 'quantity' => 1, 'clientItemReference' => 'itemRef4'],

$data['hash'] = createHash($data, $sign_secret);
$client->api('/user/123/charge', 'POST', $data);

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