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16 cookies


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16 cookies

  1. 1. Cookies Set a cookie – setcookie()Extract data from a cookie - $_COOKIE Augment user authentication script with a cookie
  2. 2. What are cookies?• Web transactions are “memory-less”• A cookie is a text file that a website stores on a client’s computer to maintain information about the client during and between browsing sessions.• Useful for: – Shopping carts – User communities – Personalized sites• Not recommended for storing sensitive data• Store a unique identification string that will match a user held securely in a database
  3. 3. Shopping example• Assign an identification variable to a user to track what he does when he visits your site1. User logs in2. Send a cookie with variables to say “This is Joe, and Joe is authenticated”3. While Joe is surfing your site, you can respond “Hello, Joe!” on every page4. If Joe clicks through your catalog and chooses 3 items to buy, you can keep track of these items5. Display the items together when Joe goes to the checkout area
  4. 4. Setting Cookies• A server can access only the cookies that it has placed on the client.• setcookie() function with parameters:1. Name – cookie name accessible in subsequent scripts2. Value – cookie value passed to name3. Expiration– (optional) sets a specific time in seconds when the cookie values is no longer accessible e.g. time() + 24*60*60*3 to expire in 3 days – A cookie without expiration is known as a session cookie, – A cookie with an expiration time is a persistent cookie.1. Path – Directories the cookie is valid – "/“ valid for all files and directories in the website – Specific directory: cookie valid for pages within that directory1. Domain- only valid for the host and domain that set them – If no domain, host name of the server that generated the cookie6. Security – – 1 or TRUE: cookie will only be transmitted via HTTPS i.e. secure web site – 0 or FALSE: non-secure
  5. 5. Example• setcookie( “id”, “55adb984523afer”, time() + 14400, “/”, “”, 0); // 4 hours
  6. 6. Bad cookie setting• Cookies defined in function setcookie are sent to the client at the same time as the information in the HTTP header; therefore, it needs to be called before any XHTML is printed.• Hence you absolutely must set a cookie before sending any other content to the browser• See m16/bad_cookie.php
  7. 7. <html> <head> <title>Bad Cookie</title> </head> <body> <?php setcookie("test", "ok", "", "/", "", 0); ?> <h1>Bad Cookie</h1> </body></html>This is an error in setting cookies.Setcookie() function should be placed before <html> tag
  8. 8. M16/bad_cookie.php
  9. 9. M16/16-1setcookie.php<?php$cookie_name = "test_cookie";$cookie_value = "test string!";$cookie_expire = time()+86400;$cookie_domain = "";setcookie($cookie_name, $cookie_value, $cookie_expire, "/" , $cookie_domain, 0);?><html><head><title>Set Test Cookie</title></head><body><h1>Mmmmmmmm...cookie!</h1></body></html>
  10. 10. M16/16-1setcookie.php
  11. 11. Permanent cookie• See fig23_16_20 from text – Cookies.html – Cookies.php – Readcookies.php
  12. 12. Input for cookies – cookies.html
  13. 13. Acknowledgment – cookies.php
  14. 14. Read cookies – readcookies.php
  15. 15. Augmenting auth_user with cookie• 16-2show_login.php – Gets login username and password – Calls 16-2do_authuser.php to authenticate the login• 16-2do_authuser.php – Checks DB to authenticate the login – If authenticated: • Set cookie for the user • displays links to – secretA.php – secretB.php
  16. 16. 16-2show_login.html
  17. 17. Authenticated!
  18. 18. Clicking on secretA or secretB link . . .• We would expect to get into the links
  19. 19. Wait! We got redirected back to the login page• Why?• Debug . . .
  20. 20. In 16-2do_authuser.php:if ($num !=0){ $cookie_name ="auth"; $cookie_value ="ok"; $cookie_expire ="0"; $cookie_domain =""; setcookie($cookie_name,$cookie_value,$cookie_expire,"/",$cookie_domain,0);The domain was we accessed it with http://localhost/m16/16-2secretB.php
  21. 21. Repeat the script in
  22. 22. Authenticated!
  23. 23. Clicking on the secretA link
  24. 24. Clicking on the secretB link
  25. 25. Check if cookie really works• Exit the session – Exit completely out of the web browser • The cookie was a session cookie • Auth cookie should now have expired – Reopen the web browser – Attempt to access 16-2secretB.php – Since the user is not authenticated anymore, the user will be redirected to the login page
  26. 26. leads to