Coinmarketcap PHP API no data returned

Just a simple test to get some data via API doensn't work. I use the PHP example from their own website, but no result is printed. Source: https://pro.coinmarketcap.com/api/v1#section/Quick-Start-Guide Is there anything I do wrong? I use the sandbox-environment with the demo API key. Curl is installed at my server. Thanks a lot!

<?php
$url = 'https://sandbox-api.coinmarketcap.com/v1/cryptocurrency/listings/latest';
$parameters = [
  'start' => '1',
  'limit' => '5000',
  'convert' => 'USD'
];

$headers = [
  'Accepts: application/json',
  'X-CMC_PRO_API_KEY: b54bcf4d-1bca-4e8e-9a24-22ff2c3d462c'
];
$qs = http_build_query($parameters); // query string encode the parameters
$request = "{$url}?{$qs}"; // create the request URL


$curl = curl_init(); // Get cURL resource
// Set cURL options
curl_setopt_array($curl, array(
  CURLOPT_URL => $request,            // set the request URL
  CURLOPT_HTTPHEADER => $headers,     // set the headers 
  CURLOPT_RETURNTRANSFER => 1         // ask for raw response instead of bool
));

$response = curl_exec($curl); // Send the request, save the response
print_r(json_decode($response)); // print json decoded response
curl_close($curl); // Close request
?>

Solution

When I var_dump($response) I'm getting:

error code: 1020

This is caused by the API detecting a bot/script.

Consider adding a user agent:
^{PHP cURL how to add the User Agent value OR overcome the Servers blocking cURL requests?}

curl_setopt_array($curl, array(
    CURLOPT_URL => $request,
    CURLOPT_HTTPHEADER => $headers,
    CURLOPT_RETURNTRANSFER => 1,
    CURLOPT_USERAGENT => 'Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0'
));

Now, the script outputs:

stdClass Object
(
    [status] => stdClass Object
        (
            [timestamp] => 2021-08-30T15:06:20.200Z
            [error_code] => 0
            [error_message] =>
            [elapsed] => 0
            [credit_count] => 1
            [notice] =>
        )

    [data] => Array
        ... and a lot more ...