I ran across a problem today trying to define a RemoteObject (mx.rpc.remoting.mxml.RemoteObject) in ActionScript instead of a services-config.xml file.

It seems like it would be fairly straightforward

 var myRo:RemoteObject = new RemoteObject();
 myRo.source = "amf_tests.HelloWorld";
 myRo.destination = "amfphp";
 myRo.endpoint = "/amfphp/gateway.php";

but, alas, I found that endpoint isn’t a property, though it looks like it might be in the future. It isn’t even a readily accessible class. You need to build a channelset, add a channel, and then pass a url (and id) to the channel to specify the endpoint. Something like this:

 myRo.channelSet(new ChannelSet().addChannel(new AMFChannel("my_amfphp", "/amfphp/gateway.php")));

The above is equivalent to the following services-config.xml (I think):

<?xml version="1.0" encoding="UTF-8"?>
<services-config>
 <services>
  <service id="amfphp-flashremoting-service" class="flex.messaging.services.RemotingService" messageTypes="flex.messaging.messages.RemotingMessage">
   <destination id="amfphp">
    <channels>
     <channel ref="my_amfphp"/>
    </channels>
    <properties>
     <source>*</source>
    </properties>
   </destination>
  </service>
 </services>
 <channels>
  <channel-definition id="my-amfphp" class="mx.messaging.channels.AMFChannel">
   <endpoint uri="/amfphp/gateway.php" class="flex.messaging.endpoints.AMFEndpoint"/>
  </channel-definition>
 <channels>
</services-config>

This explains it better than me.