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Cookies Set a cookie – setcookie() Extract data from a cookie - $_COOKIE Augment user authentication script with a cookie.

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Presentation on theme: "Cookies Set a cookie – setcookie() Extract data from a cookie - $_COOKIE Augment user authentication script with a cookie."— Presentation transcript:

1 Cookies Set a cookie – setcookie() Extract data from a cookie - $_COOKIE Augment user authentication script with a cookie

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 Shopping example Assign an identification variable to a user to track what he does when he visits your site 1.User logs in 2.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 page 4.If Joe clicks through your catalog and chooses 3 items to buy, you can keep track of these items 5.Display the items together when Joe goes to the checkout area

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 scripts 2.Value – cookie value passed to name 3.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. 4.Path – Directories the cookie is valid – "/“ valid for all files and directories in the website – Specific directory: cookie valid for pages within that directory 5.Domain- only valid for the host and domain that set them – If no domain, host name of the server that generated the cookie 6.Security – – 1 or TRUE: cookie will only be transmitted via HTTPS i.e. secure web site – 0 or FALSE: non-secure

5 Example setcookie(“id”, “55adb984523afer”, time() + 14400, “/”, “”, 0); // 4 hours

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 Bad Cookie <?php setcookie("test", "ok", "", "/", "", 0); ?> Bad Cookie This is an error in setting cookies. Setcookie() function should be placed before tag

8 M16/bad_cookie.php

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); ?> Set Test Cookie Mmmmmmmm...cookie!

10 M16/16-1setcookie.php

11 Permanent cookie See fig23_16_20 from text – Cookies.html – Cookies.php – Readcookies.php

12 Input for cookies – cookies.html

13 Acknowledgment – cookies.php

14 Read cookies – readcookies.php

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 16-2show_login.html

17 Authenticated!

18 Clicking on secretA or secretB link... We would expect to get into the links

19 Wait! We got redirected back to the login page Why? Debug...

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 When we accessed it with http://localhost/m16/16-2secretB.php

21 Repeat the script in

22 Authenticated!

23 Clicking on the secretA link

24 Clicking on the secretB link

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 leads to

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