cookies set a cookie – setcookie() extract data from a cookie - $_cookie augment user...
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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 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 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 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.
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() + 14400, “/”,“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
<html> <head> <title>Bad Cookie</title> </head>
<body> <?php setcookie("test", "ok", "", "/", "127.0.0.1", 0); ?> <h1>Bad Cookie</h1> </body></html>
This is an error in setting cookies.Setcookie() function should be placed before <html> tag
M16/bad_cookie.php
M16/16-1setcookie.php <?php$cookie_name = "test_cookie";$cookie_value = "test string!";$cookie_expire = time()+86400;$cookie_domain = "127.0.0.1";
setcookie($cookie_name, $cookie_value, $cookie_expire, "/" , $cookie_domain, 0);
?><html><head><title>Set Test Cookie</title></head><body>
<h1>Mmmmmmmm...cookie!</h1>
</body></html>
M16/16-1setcookie.php
Permanent cookie
• See fig23_16_20 from text– Cookies.html– Cookies.php– Readcookies.php
Input for cookies – cookies.html
Acknowledgment – cookies.php
Read cookies – readcookies.php
Augmenting auth_user with cookie
• 16-2show_login.php– Gets login username and password– Calls 16-2do_authuser.php to authenticate the login
• 16-2do_authuser.php– Checks DB to authenticate the login– If authenticated:
• Set cookie for the user• displays links to
– secretA.php– secretB.php
16-2show_login.html
Authenticated!
Clicking on secretA or secretB link . . .
• We would expect to get into the links
Wait! We got redirected back to the login page
• Why?• Debug . . .
In 16-2do_authuser.php:
if ($num !=0){$cookie_name ="auth";$cookie_value ="ok";$cookie_expire ="0";$cookie_domain ="127.0.0.1";
setcookie($cookie_name,$cookie_value,$cookie_expire,"/", $cookie_domain,0);
The domain was 127.0.0.1
When we accessed it with http://localhost/m16/16-2secretB.php
Repeat the script in 127.0.0.1
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
