Suffered this issue today trying enumerate a internet explorer 
window. Turns out Internet Explorer doesn't register it self with the 
"Running Object Table" so this function returns that error. 

Work arounds are to either create a Browser Helper Object that will 
add the IE instance to the ROT, or enumerate all windows via the 
Shell.Application COM and iterate through them looking for 
iexplore.exe . 

Tom

I experienced the same problem. Googling the internet I found a clue. Somebody had a likewise problem. But he noticed that it only happened when Apache was started as a service and not when Apache was started in a console. I checked this in my situation. And indeed, all works fine when you start Apache in a console. And you get the reported problem when you start Apache as a service.
Hope this gives some clue to resolving the problem.
Greets, Gerrit.

Yes.... when Apache runs as a service it runs under a different user than when you start it from the command line. You can change the user the service uses, though that does not fix it. We have had the same issues with .NET services. You just get these permission type errors no matter how much you Google for the proper settings. And Microsoft's official position on this situation is that you should not be using Excel/Word from a service. Gotta love Microsoft... hahaha.

Of course in our case we are not using Excel/Word really, I use them as an example hoping that:
- Someone can post how you fix/set these permissions to get around this, if that is the cause.
- Perhaps PHP can be enhanced to return a more complete error message. "Operation unavailable" is useless (it could mean anything, e.g. this type of operation is not available because PHP no longer supports it or because PHP module xx is not installed, who knows). Rather something like "Unable to instantiation COM Object due to insufficient user permission" would help?

I think the documentation[1] is (at least nowadays) pretty
clear on that:

| com_get_active_object() is similar to creating a new instance of
| a COM object, except that it will only return an object to your
| script if the object is already running. OLE applications use
| something known as the "Running Object Table" to allow well-known
| applications to be launched only once; this function exposes the
| COM library function GetActiveObject() to get a handle on a
| running instance.

> Rather something like "Unable to instantiation COM Object due to
> insufficient user permission" would help?

That would be guesswork on behalf of PHP, though.  You get exactly
the same result from GetActiveObject() if you have permission to
create a new Word.Application, but no instance of Word.Application
is running.

So, unless you are sure that a Word.Application is running, use
something like the following:

<?php
try {
    $obj = com_get_active_object("Word.Application");
} catch (com_exception $ex) {
    // perhaps no Word.Application running?
    $obj = new COM("Word.Application");
}
?>

[1] <https://www.php.net/com_get_active_object>