I don’t even know how this method is called, I just know the behavior I want to achieve.
My example for this is Facebook. If you go to facebook.com/[username or id] you get to the profile page, but I can’t imagine that they’re creating a directory in their root folder and putting a index file in there for every user.
So how’s the following behavior accomplished; You go to somepage.com/foo/bar/hello but actually you’re requesting somepage.com/foo?bar=hello ?
Is this even possible with Apache and PHP?
That thing is called URI/URL and the local part of it is passed to a webserver. The webserver then processes the request.
Yes. Not even even. This is what a webserver is for. What happens on the server is entirely shielded by the HTTP protocol which knows only the URI/URL specification which does not regulate if and how that needs to match to concrete processes or files on the webserver.
For example with the Apache HTTP Server there is a famous module called Mod_Rewrite that does URL-Rewriting. Often in a fashion that the user with her browser does not take any notice of it.
Example configuration with a PHP file (Apache HTTPD):
In a PHP script you can obtain the URI/URL by making use of special variables like
$_SERVER['REQUEST_URI']and$_SERVER['QUERY_STRING'].