Hi magdam1, welcome to the forums,
The book is a bit out of sync. The author didn't figure on someone wanting to try it before they read the explanation of what the code is doing.
If you look on page 112 you'll see:
All that’s left is to write the welcome.html.php template. Here it is:
followed by the code example, then
That’s it! Fire up your browser and point it at http://localhost/welcome/ (or
http://localhost:8080/welcome/ or similar if you need to specify a port number for
your web server). You’ll be prompted for your name, and when you submit the
form, you’ll see the appropriate welcome message. The URL should stay the same
throughout this process.
I'm the same way, always wanting to test things. I don't let reading get in the way of the fun stuff except as a last resort!