It is true that PHP itself can't do that, but it's also true that Java cannot do it either.
Active X "should" not be able to do it either.
It's called "frame snooping", meaning one frame can see what another frame is doing. (this is similar)
In all remotely recent browsers (that I know of), frame snooping was made nearly impossible (I know no way of doing it, but some lengthy hack may be possible).
Simply, one frame being able to look at another, while helpful for some developers, is a horrible security risk.
Thus, Microsoft/Netscape/Opera/Everybody do their best to keep it from happening.
Even more is being able to "window snoop", which is also nearly impossible as it's even a bigger security hole.
In short, you can't do it.
The only possible way would be to create a plug-in and have your user install it, use some form of applet which your client must agree to running each time you want to use it (like on those online hard drive backup thingey places...the names escape me at the moment...maybe freedrive etc).
The other way would be to find some of those old java/active x hacks, and then you could use it and have it work on old browsers.
The problem is, a large amount of security programs (and many browsers even) tag this as a major security breach, and will send up bells and whistles all over the place.
The only faster way to get rid of a user is header("Location🙂, lol.
In short, nope, not possible. ;(