Hey,
Well, first, fspassengers is coming in the next update (not sure if you read the front page). So you don't need to create scripts, etc for that. That'll be built in, using the existing scripts/platform.
That code you pasted is just verifying the form field input, from the first page of the install. Just makes sure that everything is entered.
That error usually comes when PHP5 isn't enabled properly. Perhaps you also accidentally deleted the htaccess file? Try re-uploading as well, sometimes files get corrupted when using FTP on upload.
Also, are you using the beta, or the release version? Make sure it's the release. Beta still has some problems.