There are two options. You can download and install IIS 8 Express, which is a user mode application that is basically IIS 8. This will not run if you are not logged into the computer, however.
Or, you can install IIS 8 the service, which can be installed via Programs and Features in control panel. Click on "Add or Remove Windows Components" and it's in the list. Why do you want to run IIS on a computer without an internet connection? Seems to defeat the purpose.
As for PHP, there's a lot involved with configuring it. There are lots of tutorials online about configuring IIS to use PHP.