<?php
// Require the Composer autoloader.
require 'vendor/autoload.php';

use Aws\S3\S3Client;
use Aws\S3\Crypto\S3EncryptionClientV3;

// Instantiate an Amazon S3 client.
$s3 = new S3Client([
    'version' => 'latest',
    'region'  => 'us-west-2'
]);

// Instantiate an Amazon S3 Encryption Client V3.
$client = new S3EncryptionClientV3($s3Client);

### Upload a file to Amazon S3 using client side encryption

$kmsKeyId = 'kms-key-id';
$materialsProvider = new KmsMaterialsProviderV3(
    new KmsClient([
        'profile' => 'default',
        'region' => 'us-east-1',
        'version' => 'latest',
    ]),
    $kmsKeyId
);

$bucket = 'the-bucket-name';
$key = 'the-file-name';
$cipherOptions = [
    'Cipher' => 'gcm',
    'KeySize' => 256,
    // Additional configuration options
];

$result = $client->putObject([
    '@MaterialsProvider' => $materialsProvider,
    '@CipherOptions' => $cipherOptions,
    '@CommitmentPolicy' => 'REQUIRE_ENCRYPT_REQUIRE_DECRYPT',
    '@KmsEncryptionContext' => ['context-key' => 'context-value'],
    'Bucket' => $bucket,
    'Key' => $key,
    'Body' => fopen('file-to-encrypt.txt', 'r'),
]);