Web servers, installed one: Apache. On silo, Unix.
Apache directories: htdocs (HTML), cgi-bin, conf, logs, bin. 
Write programs for Apache: Perl, Python. Keeping state. 

Lab three: set up password protected folders. Use yours to post
your homework assignments. Currently this means: Homework Two. 

Move on to new topics: MySQL and PHP. Install them. 

MySQL server allows for relational database design & management.

PHP started as a CGI script written in Perl. 

It's a platform for programming like Perl/CGI or Python/CGI.

PHP brings up the notion of server-side state (sessions). 

End the first half of the semester with an implementation of
server-side state with Perl/CGI and a database. Database access
from Perl also look into database access from Python and PHP.

-- 

state, input, constant

what is our state: 

a) changes but we need to remember it: the right answer

b) changes but we need to remember: remaining flags

c) changes but needs to be remembered: user's score

d) changes but needs to be remembered: the question number 

what is our input: 

e) can't anticipate, read from user: the answer

constants: 

f) the url: goes in the code, directly

--

So the code ended up like this: 

#!/usr/bin/perl

use CGI; 
$q = new CGI; 

@names = ("Italy", "China", "United States", "Australia", "Russia", "Brazil", "South Africa", "Spain"); 
$url = "http://silo.cs.indiana.edu:46016/images/"; 

print $q->header, $q->start_html; 

# retrieve state:

$questions = $q->param('questions'); 

$answerkey = $q->param('answerkey'); 
$userscore = $q->param('userscore'); 
$totalques = $q->param('totalques'); 

# if state is empty: 
if (! $questions) { # initialize the state
  $userscore = 0; 
  $totalques = 0; 
  $answerkey = ""; 
  $questions = join(',', @names);
  $message = "Are you ready? Score now: $userscore / $totalques "; 
} else { # otherwise: read the input, update the state 
  $answer = $q->param('answer'); 
  if ($answerkey) { # do grading, when appropriate 

  } else {

  } 
  @questions = split(/,/, $questions, 2); 
  $answerkey = $questions[0]; 
  $questions = $questions[1]; 
  $message = "What flag is this: <img src=\"" . $url . $answerkey . ".png\"> ?";
} 


print qq{
  <form> 
    $message 
    <input type="hidden" name="questions" value="$questions"> 
    <input type="hidden" name="answerkey" value="$answerkey"> 
    <input type="hidden" name="userscore" value="$userscore"> 
    <input type="hidden" name="totalques" value="$totalques"> 
    <p> Press <input type="submit" name="proceed" value="Proceed"> when ready. 
  </form> 
}; 

print $q->end_html;