如何使用Composer解决AmazonPayAPI集成问题，并提升支付处理效率

<code>composer require amzn/amazon-pay-api-sdk-php</code>

<code class="php"><?php
include 'vendor/autoload.php';
echo "SDK_VERSION=" . Amazon\Pay\API\Client::SDK_VERSION . "\n";
?></code>

<code class="php"><?php
include 'vendor/autoload.php';

$amazonpay_config = array(
    'public_key_id' => 'YOUR_PUBLIC_KEY_ID',
    'private_key'   => 'keys/private.pem',
    'region'        => 'YOUR_REGION_CODE',
    'sandbox'       => true,
    'algorithm'     => 'AMZN-PAY-RSASSA-PSS-V2',
);

$payload = array(
    'webCheckoutDetails' => array(
        'checkoutReviewReturnUrl' => 'https://localhost/store/checkout_review',
        'checkoutResultReturnUrl' => 'https://localhost/store/checkout_result'
    ),
    'storeId' => 'amzn1.application-oa2-client.000000000000000000000000000000000'
);
$headers = array('x-amz-pay-Idempotency-Key' => uniqid());

try {
    $client = new Amazon\Pay\API\Client($amazonpay_config);
    $result = $client->createCheckoutSession($payload, $headers);
    if ($result['status'] === 201) {
        $response = json_decode($result['response'], true);
        $checkoutSessionId = $response['checkoutSessionId'];
        echo "checkoutSessionId=$checkoutSessionId\n";
    } else {
        echo 'status=' . $result['status'] . '; response=' . $result['response'] . "\n";
    }
} catch (\Exception $e) {
    echo $e . "\n";
}
?></code>