(PHP Extension) S3 Get Object Metadata, such as ETag

Demonstrates how to get an S3 object's metadata using a HEAD request.

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<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$rest = new CkRest();

// Connect to the Amazon AWS REST server in the desired region.
// In this case we connect to S3 in the "us-west-2" region.
$bTls = true;
$port = 443;
$bAutoReconnect = true;
$success = $rest->Connect('s3-us-west-2.amazonaws.com',$port,$bTls,$bAutoReconnect);

// Provide AWS credentials.
$authAws = new CkAuthAws();
$authAws->put_AccessKey('AWS_ACCESS_KEY');
$authAws->put_SecretKey('AWS_SECRET_KEY');
$authAws->put_ServiceName('s3');

// This particular bucket is in the Oregon region, as opposed to the US Standard,
// therefore the Region must be set appropriately.
// Also note that we connected to "s3-us-west-2.amazonaws.com".
$authAws->put_Region('us-west-2');

$success = $rest->SetAuthAws($authAws);

// Note: The above REST connection and setup of the AWS credentials
// can be done once.  After connecting, any number of REST calls can be made.
// The "auto reconnect" property passed to rest.Connect indicates that if
// the connection is lost, a REST method call will automatically reconnect
// if needed.
// --------------------------------------------------------------------------

// Set the bucket name via the HOST header.
// In this case, the bucket name is "chilkat.ocean".
// Note that the Host header should use "bucketName.s3.amazonaws.com", not "bucketName.s3-us-west-2.amazonaws.com"
$rest->put_Host('chilkat.ocean.s3.amazonaws.com');

// Our object is "starfish.jpg".
// Get the metadata.
// Since we are sending a HEAD request, we shouldn't use any of the Full* methods.
// Instead, send the request, then just read the response header.
$success = $rest->SendReqNoBody('HEAD','/starfish.jpg');
if ($success != true) {
    print $rest->lastErrorText() . "\n";
    exit;
}

// Now get the response header.
$statusCode = $rest->ReadResponseHeader();
if ($statusCode < 0) {
    print $rest->lastErrorText() . "\n";
    exit;
}

// When successful, the S3 Storage service will respond with a 200 response code,
// with an XML body.  
if ($statusCode != 200) {
    // Examine the request/response to see what happened.
    print 'response status code = ' . $statusCode . "\n";
    print 'response status text = ' . $rest->responseStatusText() . "\n";
    print 'response header: ' . $rest->responseHeader() . "\n";
    exit;
}

// The response header contains information about the S3 object.
// For example:

// 	HTTP/1.1 200 OK
// 	x-amz-id-2: GrV/hrB2EUkBlWc0h3JDdmVIrYDXfPC7CGvo/qSVRmYRPwilAOry8+4r2YWl4xJfa1HRYXrP808=
// 	x-amz-request-id: 4BDC6D6AEA0BDEF3
// 	Date: Mon, 13 May 2019 22:03:13 GMT
// 	Last-Modified: Mon, 10 Nov 2014 16:10:23 GMT
// 	ETag: "2e9c59dbf2662367dc97dfdda85da048"
// 	Accept-Ranges: bytes
// 	Content-Type: image/jpg
// 	Content-Length: 6229
// 	Server: AmazonS3

// Get the ETag response header value:
$etag = $rest->responseHdrByName('ETag');
print 'ETag: ' . $etag . "\n";

?>