function createAllParams(string $id, string $token, string $secret, int $timestamp, string $identifier, string $type, array $parameters, string $actionId): string
{
	// in alphabetical order
	$fields['accesstoken'] = $token;
	$fields['actionid'] = $actionId;
	$fields['identifier'] = $identifier;
	$fields['resourceid'] = $id;
	$fields['secret'] = $secret;
	$fields['timestamp'] = $timestamp;
	$fields['type'] = $type;

	// please use an ordered data structure (such as a linked list) here since ksort is not recursive.
	ksort($parameters);

	// PHP defaults of json_encode() are being used here
	$parametersBundled = json_encode($parameters);
	$fieldsBundled = implode(',', $fields);
	$allParams = $parametersBundled.','.$fieldsBundled;

	return $allParams;
}


function createHmac(string $secret, string $allParams): string
{
	// PHP md5 without second parameter (as used here) does return
	// the hexadecimal representation __as lowercase string__, not binary!

	return md5($secret.md5($allParams));
}
$token = '4a9c9t9c9d34dac46d';
$secret = '9348938afdef0293838475934875983475';
$timestamp = '1566393693'; // `date +%s` on shell

$testParameters = [
	'testParam-string' => "teststring 你好 <tag></tag> äöüß \" ' & \r\n",
	'testParam-null' => null,
	'testParam-float' => ".12387548574875847584593475", //floats have to be given as strings
	'testParam-int' => 3,
	'testParam-array-assoc' => [
		'key8' => 'firstEntry',
		'key1' => 'lastEntry',
	],
	'testParam-array-numerical' => ['hello', 'world'],
];

echo "\$testParameters: \n<br>".var_export($testParameters, true)."\n\n";
// output: array ( 'testParam-string' => 'teststring 你好 äöüß " \' & ', 'testParam-null' => NULL, 'testParam-float' => 0.1238754857487584792874457662037457339465618133544921875, 'testParam-int' => 3, 'testParam-array-assoc' => array ( 'key8' => 'firstEntry', 'key1' => 'lastEntry', ), 'testParam-array-numerical' => array ( 0 => 'hello', 1 => 'world', ), )

echo "<br><br>\$allParams:\n<br>";
$allParams = createAllParams('testID', $token, $secret, $timestamp, 'testIdentifier', 'testResourceType', $testParameters, 'testActionId');
echo "$allParams\n\n";
/*
output (one line):
{"testParam-array-assoc":{"key8":"firstEntry","key1":"lastEntry"},"testParam-array-numerical":["hello","world"],"testParam-float":0.12387548574876,"testParam-int":3,"testParam-null":null,"testParam-string":"teststring \u4f60\u597d <tag><\/tag> \u00e4\u00f6\u00fc\u00df \" ' & \r\n"},4a9c9t9c9d34dac46d,testActionId,testIdentifier,testID,9348938afdef0293838475934875983475,1566393693,testResourceType
*/
echo "<br><br>HMAC:\n";
echo createHmac($secret, $allParams)."\n";
// output: bacf778f99c99a3e78745ad72373e337