Php registration script and ipv4 to ipv6 tunnel

this is a project for my school due to next week.

the project consist on developing a web server which the user accesses, registers and login, for then requesting the service of an ipv6 over ipv4 tunnel for his network. the server connects to the cisco router 1841, which gives you access to the internet, via telnet and configures the tunnel endpoint; then I present on screen the commands for the user to set their endpoint on the pc, by default for windows...
this part I have complete, though now the username and the e-mail are giving me an error in the register... this I would like you to check and correct

i would send you a rar archive with all the scripts...

now I need to detect the user's os (linux, mac or windows) for presenting the correct commands and create a .bat or .sh file for the user to run it...
I already detect the os and create de file, but I need a condition for letting the user download the .bat or .sh file depending on its os

when you login, you can see your profile and check if your session is active... I would like to add a counter saying how many sessions this users has created...
I would also like to view the number of active sessions and its users on the main page...

can you do that completely and working properly for a max of 4 days?

The project is on this webpage http://spotgrouprd.org/odette/