amazonwebservices/aws-sdk-for-php — pull request #32 by odracci (2012-07-09 23:25:44+00:00)
Title: change_content_type() doesn't update the Content-type.

From the proposal (http://doc.s3.amazonaws.com/proposals/copy.html):

COPY: Copy the metadata from the original object. If this is specified,
any metadata in this request will be ignored. This is the default.
REPLACE: Ignore the original object’s metadata and replace it with the
metadata in this request.

With metadataDirective = REPLACE it works.