Running php script with "?var=string" query inside another php script

I am trying to run a php script with query from wthin another php script. I have a php script that adds information to a database and calls another php script with query to view those details using the include command but I keep getting an error "Failed opening" file. Is there anyway of running a php script with the "?var=string" query inside another php script ??? Any help would be much appreciated. Dave