check if a file is included

I have a file called interceptor.php, which I would like to make use of in two ways 1. either call it directly from the browser or 2. included from another file I know I could use something like this to see if it was called via a url like http://www.site.com/interceptor.php : if (strstr('interceptor',$__SERVER["REQUEST_URI"])) { // url } else { //probably included } but I would like to know if there is a neater, cleaner, sparkly way of doing this. Thanks Clive