That is a dangerous piece of code. What if I request:
http://hostname/punisher.php?file=/etc/passwd
You guessed it! I can see all the valid users on your system. There are many other files I can see also.
Please don't use this code!!!
You should sanitize the vars before using them, or else you might get hacked
If I hadn't seen the code, it wouldn't be as easy to snoop your system. But smart hackers/crackers will test a bunch of stuff to see what works.
I hope everyone understands how serious this can be!
I'd edit this post Mojo and remove the code before others use it.