If the connection succeeds, the remote webservice may still be so slow that you want to abort the request. If you send a request and do not get a reply within some time, you may want to inform the user that you have given up. The setting default_socket_timeout configures this: if there is no activity on the socket within this timeout, the request is aborted. This works both for the WSDL as the SOAP requests, but only for HTTP and not for HTTPS (PHP bug #41631).