gistfile1.m

var connection = [[CPURLConnection alloc] initWithRequest:[CPURLRequest requestWithURL:"whatever.php?parameter=blah&etc=yadadada"] delegate:self startImmediately:NO];
[connection start];


...


- (void)connection:(CPURLConnection)aConnection didReceiveData:(CPString)data
{
    if (connection == aConnection)
    {
        try
        {
            var result = CPJSObjectCreateWithJSON(data);
        }
        catch(e)
        {
            return [self connection:aConnection didFailWithError: e];
        }

        // do stuff with result
    }
}

- (void)connection:(CPURLConnection)aConnection didFailWithError:(CPError)anError
{
    [self connectionDidFinishLoading:aConnection];
}

- (void)connectionDidFinishLoading:(CPURLConnection)aConnection
{
    if (connection == aConnection)
    {
        connection = nil;
    }
}