(PECL getdns >= 0.10.0)
php_getdns_context_set_dns_transport_list — Set the ordered list of transports that will be used for DNS lookups.
This function sets the ordered list of transports that will be used for DNS lookups. If only one transport value is specified it will be the only transport used. Basic resolution will fail if that transport option is not available. Fallback transport options are specified by including multiple values in the list.
The previously created DNS context that is to be used with this request.
The number of elements contained in the array of transport values.
An indexed array of transport values. Valid values include GETDNS_TRANSPORT_UDP, GETDNS_TRANSPORT_TCP, GETDNS_TRANSPORT_TLS, and GETDNS_TRANSPORT_STARTTLS. The default is a list containing GETDNS_TRANSPORT_UDP followed by GETDNS_TRANSPORT_TCP.
This function returns an integer response code. GETDNS_RETURN_GOOD indicates successful completion.