Sorry. I've had to sit and think about this for awhile. Basically, you're making a policy decision in code, which is to guarantee that we will be able to support point releases where phpVBoxVer > VBoxVer. I don't think this is necessarily true. Each point release has its own endpoint/lib/vboxweb(service)-X.Y.wsdl and we currently don't load a separate one depending on the point release.

I understood. I think that the vitrualbox project when publish a new version, exemple virualbox 5.3, all files had a retrocompatibility with previous versions 5.2, 5.1 and 5.0. Then, the endpoint/lib/vboxweb(service)-5.3.wsdl should be retrocompatible too.

But, this is not a rule.

Yes, and although they've been largely compatible so far, there have also been unexpected changes, so we've taken to checking it each time. I had considered keeping the old wsdl files around for awhile and loading them depending on the VBox version. That would acheive the same aim. Something like if(!file_exists("endpoints/lib/vboxweb-$x.$y.wsdl") || !file_exists("endpoints/lib/vboxwebservice-$x.$y.wsdl") { ... alert ...}

The other changes are good, though. I'd also suggest using isset() for ports as well for symmetry. That way the config will become simpler.

I think that vrdeport is required and not can't be omitted. But I'll check this.

About version issue, have more than 1 version of wsdl files can be confuse, especially when has multi vbox servers.

We can have a default vrdeport (9000-9100) when it's omitted.

When there are multiple vbox servers you can only log into them one at a time, so we could still detect the version after logging in and verify the same way we do now.

I changed the default vrdeaddress to empty, because it is the default of vbox. And has been removed the ISSET(), because is not more necessary.

The default vbox vrdeport is 3389. But, phpvirutalbox the default port actually is 3390-5000. I don't think so interesting change this value because that can be to interfere on old users.