Slide môn học PHP session 7 working with cookies

What are Cookies? Websites use cookies to store user-specific information  Cookies are stored on the hard disk of the Web browser  User information and preferences are send between We

Working with Cookies

Session 16

 Database APIs allows the developers

to write applications that are

easily accessible between the

database products

accessing data from the database

server

Review - I

What are Cookies?

 Websites use cookies to store

user-specific information

 Cookies are stored on the hard

disk of the Web browser

 User information and preferences

are send between Web browser and

Web server

Static Web Pages

 When a Web browser requests for a static Web page, the server responds by sending the Web page the browser requested for

 No user interaction

Dynamic Web Pages

and record it for further processing

Types of Cookies

 Persistent - Remains stored in

the Web browser for a period

specified during the time of it’s

creation

 Non-persistent - Deleted from the

Web browser as soon as the user

closes the browser

Common Uses of Cookies

 Enable websites determine:

 Number of times the user has visited the website

 Number of new visitors

 Number of regular users

 Frequency of a visitor visiting the website

 Store the date that a user last visited the website

 Maintain a customized Web page settings for a user

Working with Cookies

 Web servers and Web browsers send

each other cookies in HTTP

headers

 Web server sends the cookie in a

Set-Cookie header field

 Set-Cookie is a part of HTTP

response

Setting a Cookie

 Refers to sending the cookie to the browser

 PHP uses two functions to set a

cookie, such as:

 setcookie(): Sends cookie with urlencoding

 setrawcookie(): Sends cookie without

urlencoding

setcookie() Function

 Generates a correct header field

that is sent along with the rest of the header information

 Syntax:

setcookie(name, value, expire, path, domain, secure)

Example of setcookie() Function

setcookie("mycookie", $mapname,

time()+86400, "/webmap/", ".webworldmaps.com");

Where,

 mycookie - Name of the cookies

 time()+3600 - Time when the cookie will expire

 /webmap – Path where the cookie will be stored

Retrieving Cookie Value

 PHP provides three ways of

retrieving a cookie value:

 Passing a variable as cookie name

 Using $_COOKIE[]

 Using $HTTP_COOKIE_VARS[]

Passing Variable as Cookie Name

 Use the variable as the cookie

name

 Syntax:

echo $cookie_name

 PHP searches all the variables

present in the client computer

 Works only when the

Using $_COOKIE[]

 Requires PHP 4.1

 Simpler and more secured than

using the $HTTP_COOKIE_VARS[]

 Syntax:

$_COOKIE[‘$cookie_name’]

Using $HTTP_COOKIE_VARS[]

 Global variable that reads a value

of the cookie

 PHP passes the name of the variable

as the key to the

$HTTP_COOKIE_VARS[] array

 Syntax:

$HTTP_COOKIE_VARS[$cookie_name];

Deleting a Cookie - I

 Similar to setting a cookie

 Two ways to delete a cookie:

 Resetting the expiry time of the cookie to a

time in the past

 Resetting the cookie by specifying the name of

the cookie

Deleting a Cookie - II

 Example to delete a cookie with a

date in the past:

setcookie ("$cookie_name", "",

time()-8000);

 Example to delete Cookie by

specifying the name of the cookie:

setcookie($cookie_name);

Drawbacks of Cookies - I

 Cookies are not considered secured and reliable

 Some of the drawbacks of cookies:

 Cookies cannot contain more than a certain amount of

Drawbacks of Cookies - II

 Some users disable cookies while accessing

websites

 There can be multiple persons using the same

computer visiting the same website

 Cookies need to be called on each Web page

Summary - I

user-specific information

browser’s hard disks

send to and from the Web browser

 Persistent

Summary - II

 PHP provides three ways of

retrieving a cookie value:

 Passing a variable as cookie name

 Using $_COOKIE[]

 Using $HTTP_COOKIE_VARS[]

 PHP uses two functions to set a

cookie, such as

Summary - III

 Two ways to delete a cookie:

 Drawbacks of cookies: