require_once('vendor/autoload.php');

 require_once 'lib/Shift4/Util/Shift4Autoloader.php';
 \Shift4\Util\Shift4Autoloader::register();

use Shift4\Shift4Gateway;
use Shift4\Exception\Shift4Exception;

$gateway = new Shift4Gateway('sk_test_[YOUR_SECRET_KEY]');

$request = [
    'amount' => 499,
    'currency' => 'EUR',
    'card' => [
        'number' => '4242424242424242',
        'expMonth' => 11,
        'expYear' => 2022
    ]
];

try {
    $charge = $gateway->createCharge($request);

    // do something with charge object - see https://dev.shift4.com/docs/api#charge-object
    $chargeId = $charge->getId();

} catch (Shift4Exception $e) {
    // handle error response - see https://dev.shift4.com/docs/api#error-object
    $errorType = $e->getType();
    $errorCode = $e->getCode();
    $errorMessage = $e->getMessage();
}