Cant use the upload of the s3 service

[ITOoscarestupinan]

Hello everyone,

I'm having an issue, i'm trying to upload a file to an amazon s3 server.

$pdf=$rootdir . '/../web/uploads/pdf/'.$reference.'.pdf';
$s3 = $this->container->get('aws_s3');
$bucket = 'my-bucket';
$headers = $s3->get_object_headers($bucket, $pdf);
var_dump($headers->header['content-type']);
$response = $s3->update_object($bucket, $pdf, array(
'acl' => AmazonS3::ACL_PUBLIC,
'headers' => array(
'Content-Encoding' => 'UTF-8'
),
'meta' => array(
'Cache-Control' => 'Public',
'Max-Age' => '604800',
),
));
var_dump($response->isOK());

But always send me this error:

Warning: Cannot unset offset in a non-array variable in /root/dir/to/my/vendor/amazonwebservices/aws-sdk-for-php/services/s3.class.php line 1881

What i'm doing wrong? i take the example from here : http://docs.aws.amazon.com/AWSSDKforPHP/latest/#m=AmazonS3/update_object

Hope someone could help me.