s3-check-sse.php

<?php
// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: MIT-0 (For details, see https://github.com/awsdocs/amazon-s3-developer-guide/blob/master/LICENSE-SAMPLECODE )

require 'vendor/autoload.php';

use Aws\S3\S3Client;

$bucket = '*** Your Bucket Name ***';
$keyname = '*** Your Object Key ***';
            
$s3 = new S3Client([
    'version' => 'latest',
    'region'  => 'us-east-1'
]);

// Check which server-side encryption algorithm is used.
$result = $s3->headObject([
    'Bucket' => $bucket,
    'Key'    => $keyname,
]);
echo $result['ServerSideEncryption'];