Bucket Headers giving 403 error

[iit2011081]

I am trying to retrieve all the content from s3 bucket but is throwing 403 status code.
$s3 = new AmazonS3(array('key' => AWS_S3_KEY, 'secret' => AWS_S3_SECRET));
$options = array('prefix' => $bucket_path); // In this case $bucket_path = '';
$bucket = $s3->get_bucket_headers($bucket_name, $options);

but $bucket->status is showing 403.