Creating Databases for Web Applications

1
Creating Databases for Web Applications

• Persistent information. Cookies. Session
• Homework Examine a computer (your own or in a
  lab) for cookies and shared objects. Experiment
  with cookie programs. Read article.

2
Persistent data (aka state information)

• Data that lasts longer than one loading of an
  html page
• Store information on the server
• File
• Database
• Store information on the client computer
• Cookie
• Flash terminology SharedObject
• Keep information for the session by sending and
  re-sending it with the HTTP headers
• Php session construct

3
Cookies

• Meant to be disarming name
• Small file stored on client computer accessible
  by programs on the same domain (some limitations
  possible here), with some time limits
• YOUR computer
• PROMISE that these files don't do harm. There
  have been 'leaks' on IE
• Cookies can be set by program running on client
  (e.g., JavaScript) or server (e.g., php)

4
Marketing

• Cookies, web beacons, Flash SharedObjects are
  used frequently for marketing purposes.
• HomeworkCathy Dwyer articlehttp//csis.pace.edu
  /dwyer/research/AMCISDwyer2009.pdf

5
Show cookies

• FireFox Tools Options Privacy Show Cookies
• IE Tools Internet Options General Settings
  (under Browsing history) View files
• ???

6
Flash player

• Settings manager for new sites
• http//www.macromedia.com/support/documentation/en
  /flashplayer/help/settings_manager03.html
• Settings for sites already visited (trust that
  list is complete?)
• http//www.macromedia.com/support/documentation/en
  /flashplayer/help/settings_manager07.html117717

7
Browser (user) limits

• Your user/customer/player/client may choose to
  forbid all cookies or
• Make decision case by case.
• Note most people don't do this, but designers
  should make plans
• Retain information some other way
• php session, store information on server, ?
• Make user re-enter information
• Cookies are browser specific. If you visit a site
  using IE and set cookies and then Firefox, it
  won't pick up the cookie

8
Setting and using cookies

• Required
• Name
• Value
• Optional
• expires. Time from a base time. JavaScript uses
  milliseconds. PHP uses seconds! Default is the
  end of the browser session
• path. Default is path of calling document
• Would allow other scripts in the document
  directory. If you want to restrict it further,
  put in more information "/Jeanine/db/"
• domain. Default is domain of this document
• By setting domain to purchase.edu, I can allow
  scripts from newmedia.purchase.edu AND
  www.purchase.edu, etc.
• secure. True requires secure transmission

9
Javascript

• document.cookie mycookie
• Where mycookie is a string like a query string,
  consisting of cookienamecookievaluepath
• domain
• secure.
• NOTE cookiename and cookievalue are your name
  and value.

10
JavaScript example

• http//newmedia.purchase.edu/Jeanine/cookie.html
• Examine source code
• The setcookie and getcookie functions are much
  more general than needed.
• Code uses the conditional operator and also the
  construct (expires). Does this value exist (is it
  set)?
• Expiration is a year from now
• 365 24 60 60 1000

milliseconds
11
PHP cookies

• setcookie(name, value, expires,path,domain,secure)
  where the last 4 are optional
• NOTE actually, the last 5 are optional. To
  delete a cookie with the name blahsetcookie(blah)
  
• CAUTION setcookie must occur before any HTML
  produced (print, echo).
• Watch out for blank lines!

12
cookies.php

• No expiration time set. Expires when browser is
  closed.
• One file form and handler of form
• Outline
• If form submitted
• Set cookie
• Welcome message
• Else get cookies already set (if they exist)
• display form

13

• lt?php
• submitted_POST'submitted'
• if (_at_(submitted))
• cname_POST'cname'
• type_POST'type'
• setcookie("ccname",cname)
• setcookie("ctype",type)
• ?gt
• lthtmlgtltheadgtlttitlegtUse cookie lt/titlegtlt/headgt
• ltbodygt
• lth1gt Welcome
• lt?
• print ("cname! lt/h1gt\n")
• print ("ltbrgtYou like type cookies.")
• ?gt
• ltbodygt lt/htmlgt
• lt?

14

• else
• ccname_COOKIE'ccname'
• ctype_COOKIE'ctype'
• ?gt
• lthtmlgtltheadgtlttitlegtForm for cookies
  lt/titlegtlt/headgt ltbodygt
• ltform action"cookies.php" methodpostgt
• Your name ltinput typetext name'cname'
• value'lt?print (_at_ccname) ?gt'gt ltbrgt
• Your favorite cookie ltinput typetext
  name'type'
• value'lt? print (_at_ctype) ?gt'gt ltbrgt
• ltinput typehidden name'submitted' valueTRUEgt
• ltinput typesubmit value'send info'gtltinput
  typereset value'reset'gt
• lt/formgt lt/bodygt lt/htmlgt
• lt? ?gt

15
cookies5min.php

• Note the cookies.php cookies may expire quicker
  or longer than this one.
• If you use both, what happens???
• Expiration is given in SECONDS!!!!
• This code also prints out the time in
  milliseconds, just for fun.
• setcookie("ccname",cname,time()560)
• setcookie("ctype",type, time()560)

16
Homework

• Write (set) and read cookies!
• Read Cathy Dwyer article
• Use tools to examine cookies on your own computer
• Prepare to discuss
• Keep working on enhancements to basic projects