PHP - include a php file and also send query parameters

You could do something like this to achieve the effect you are after:

$_GET['id']=$somevar;
include('myFile.php');

However, it sounds like you are using this include like some kind of function call (you mention calling it repeatedly with different arguments).

In this case, why not turn it into a regular function, included once and called multiple times?

Imagine the include as what it is: A copy & paste of the contents of the included PHP file which will then be interpreted. There is no scope change at all, so you can still access $someVar in the included file directly (even though you might consider a class based structure where you pass $someVar as a parameter or refer to a few global variables).