AWS AssumeRole authorization not working

Question

I am attempting to call the AssumeRole function using AWS sts in my PHP program since I want to create temporary credentials to allow a user to create an object for an AWS b

Answer 1

Maybe you should assign your sts region and endpoint:

$sts = StsClient::factory(array(
    //...      
    'region'   => 'us-west-2',                                                                                                                                                                              
    'endpoint' => 'https://sts.us-west-2.amazonaws.com', 
));