I've been looking the documentation about environment variables and see that you are able to configure credentials, regions, and profiles using environment variables, but I do not see a way to configure the endpoint url option to point to our internal proxy.

My suggestion is to configure the endpoint url if either the AWS_<REGION>_<SERVICE>_ENDPOINT or AWS_<SERVICE>_ENDPOINT (in that order of priority) environment variables are available.

I suggest making this change in one of these locations (that I have found so far) in order of suggestion preference:

• Aws\ClientResolver::_default_endpoint_provider
• Aws\Endpoint\PartitionEndpointProvider::getPartition

For reference purposes:

• Aws\Credentials\CredentialsProvider use of environment variables
• PHP getenv Documentation