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

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

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

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

Example setcookie(“id”, “55adb984523afer”, time() , “/”, “yourdomain.com”, 0); // 4 hours

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

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

M16/bad_cookie.php

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!

M16/16-1setcookie.php

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

Input for cookies – cookies.html

Acknowledgment – cookies.php

Read cookies – readcookies.php

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

16-2show_login.html

Authenticated!

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

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

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

Repeat the script in

Authenticated!

Clicking on the secretA link

Clicking on the secretB link

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

leads to