This document discusses cookies and sessions in PHP. Cookies are used to maintain state between HTTP requests and can store a small amount of text data in the user's browser. Sessions serve the same purpose as cookies but store data on the server rather than in the browser. The document demonstrates how to create, access, and destroy both cookies and sessions in PHP code. It also compares the key differences between cookies and sessions, such as cookies persisting after the browser closes while sessions do not.

1. Introduction to PHP
Web programming
Week 11, day2

2. Cookies

3. Cookies
• HTTP is a stateless protocol; this means that the web server does not know
(or care) whether two requests comes from the same user or not; it just
handles each request without regard to the context in which it happens.
• Cookies are used to maintain the state in between requests—even when
they occur at large time intervals from each other.
• Cookies allow your applications to store a small amount of textual data
(typically,4-6kB) on a Web client browser.
• There are a number of possible uses for cookies, although their most
common one is maintaining state of a user

4. Creating cookie
• setcookie(‚userid", "100", time() + 86400);
• This simply sets a cookie variable named ‚userid‛ with value ‚100‛
and this variable value will be available till next 86400 seconds
from current time
Cookie variable name
variable value
Expiration time.

5. Accessing Cookies
• echo $_COOKIE*’userid’+; // prints 100
• Cookie as array
– setcookie("test_cookie[0]", "foo");
– setcookie("test_cookie[1]", "bar");
– setcookie("test_cookie[2]", "bar");
• var_dump($_COOKIE*‘test_cookie’+);

6. Destroying Cookies
• There is no special methods to destroy a cookie, We achieve it by
setting the cookie time into a past time so that it destroys it
–Eg : setcookie(‘userid’,100,time()-100);

7. Sessions

8. Sessions
• Session serve the same purpose of cookies that is sessions are used
to maintain the state in between requests
• Session can be started in two ways in PHP
1. By changing the session.auto_start configuration setting in php.ini
2. Calling session_start() on the beginning of each pages wherever you
use session(Most common way)
Note: session_start() must be called before any output is sent to the browser

9. Creating and accessing session
• Once session is started you can create and access session variables
like any other arrays in PHP
– $_SESSION[‘userid’+ = 100;
– echo $_SESSION*‘userid’+; //prints 100
Session variable name variable value

10. Destroying session
• There are two methods to destroy a session variable
1. Using unset() function
• Eg unsset($_SESSION*‘userid’+)
2. Calling session_destroy() method. This will effectively destroy all the
session variables. So for deleting only one variable you should go for
the previous method
• Session_destroy()

11. Comparison
 cookies are stored in the user's
browser
 A cookie can keep information in the
user's browser until deleted by user or set
as per the timer. It will not be destroyed
even if you close the browser.
 Cookies can only store string
 we can save cookie for future reference
 Sessions are stored in server
 A session is available as long as the
browser is opened. User cant disable the
session. It will be destroyed if you close the
browser
 Can store not only strings but also
objects
 session cant be.
Cookies Session

12. HTTP Headers

13. Headers - Redirection
• The most common use of headers is to redirect the user to another
page. To do this,we use the Location header:
Eg: header("Location: http://phparch.com");
• header() must be called before any other output, including any
whitespace characters outside of PHP tags, as well as all HTML
data.
• If you fail to abide by this rule, two things will happen: your
header will have no effect, and PHP may output an error.

14. Questions?
‚A good question deserve a good grade…‛

15. End of day

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