Slide môn học PHP session 7 working with cookies

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Working with Cookies Session 16 Review - I     Database APIs allows the developers to write applications that are easily accessible between the database products PHP supports MySQL database for accessing data from the database server MySQL does not have its own APIs mysql_connect() function connects with the MySQL server PHP / Session 16 / Slide of 24 Review - II  Functions used with the database are:      mysql_list_dbs() mysql_select_db() mysql_list_tables() mysql_num_rows() Data access functions of MySQL are:     mysql_query() mysql_fetch_array() mysql_fetch_row(), mysql_fetch_field() PHP / Session 16 / Slide of 24 Objectives     Set a cookie Retrieve PHP cookie Delete a cookie Cookie security issues PHP / Session 16 / Slide of 24 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 PHP / Session 16 / Slide of 24 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 PHP / Session 16 / Slide of 24 Dynamic Web Pages   Require user interaction Take in information from the user and record it for further processing PHP / Session 16 / Slide of 24 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 PHP / Session 16 / Slide of 24 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 PHP / Session 16 / Slide of 24 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 PHP / Session 16 / Slide 10 of 24 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 PHP / Session 16 / Slide 11 of 24 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) PHP / Session 16 / Slide 12 of 24 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 webworldmaps.com – Domain that the cookie will use PHP / Session 16 / Slide 13 of 24 Retrieving Cookie Value  PHP provides three ways of retrieving a cookie value:  Passing a variable as cookie name  Using $_COOKIE[]  Using $HTTP_COOKIE_VARS[] PHP / Session 16 / Slide 14 of 24 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 ‘register_globals’ is disabled in the configuration file PHP / Session 16 / Slide 15 of 24 Using $_COOKIE[]    Requires PHP 4.1 Simpler and more secured than using the $HTTP_COOKIE_VARS[] Syntax: $_COOKIE[‘$cookie_name’] PHP / Session 16 / Slide 16 of 24 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]; PHP / Session 16 / Slide 17 of 24 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 PHP / Session 16 / Slide 18 of 24 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); PHP / Session 16 / Slide 19 of 24 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 information Only a maximum of 20 cookies of a domain can be maintained A browser can maintain a maximum of 300 cookies Storing large number of cookie files slows down the computer PHP / Session 16 / Slide 20 of 24 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  PHP / Session 16 / Slide 21 of 24 Summary - I     Websites use cookies to store userspecific information Cookies are stored on the Web browser’s hard disks User information and preferences are send to and from the Web browser Types of cookies:    Persistent Non-persistent Web server sends the cookie in a SetCookie header field PHP / Session 16 / Slide 22 of 24 Summary - II  PHP provides three ways of retrieving a cookie value:     Passing a variable as cookie name Using $_COOKIE[] Using $HTTP_COOKIE_VARS[] PHP uses two functions to set a cookie, such as   setcookie() setrawcookie() PHP / Session 16 / Slide 23 of 24 Summary - III  Two ways to delete a cookie:    Resetting the expiry time of the cookie to a time in the past Resetting the cookie by specifying the name of the cookie Drawbacks of cookies:      Cookies cannot contain more than a certain amount of information Only a maximum of 20 cookies of a domain can be maintained A browser can maintain a maximum of 300 cookies Some users disable cookies while accessing websites Storing large number of cookie files slows down the computer PHP / Session 16 / Slide 24 of 24 [...]... maximum of 300 cookies Storing large number of cookie files slows down the computer PHP / Session 16 / Slide 20 of 24 Drawbacks of Cookies - II Some users disable cookies while accessing websites  There can be multiple persons using the same computer visiting the same website  Cookies need to be called on each Web page  PHP / Session 16 / Slide 21 of 24 Summary - I     Websites use cookies to store... the browser PHP uses two functions to set a cookie, such as:  setcookie(): Sends cookie with urlencoding  setrawcookie(): Sends cookie without urlencoding PHP / Session 16 / Slide 11 of 24 setcookie() Function   Generates a correct header field that is sent along with the rest of the header information Syntax: setcookie(name, value, expire, path, domain, secure) PHP / Session 16 / Slide 12 of 24... cookie with a date in the past: setcookie ("$cookie_name", "", time()-8000); Example to delete Cookie by specifying the name of the cookie: setcookie($cookie_name); PHP / Session 16 / Slide 19 of 24 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 information Only a maximum of 20 cookies. .. the cookie PHP passes the name of the variable as the key to the $HTTP_COOKIE_VARS[] array Syntax: $HTTP_COOKIE_VARS[$cookie_name]; PHP / Session 16 / Slide 17 of 24 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 PHP / Session 16 / Slide 18 of... mycookie - Name of the cookies time()+3600 - Time when the cookie will expire /webmap – Path where the cookie will be stored webworldmaps.com – Domain that the cookie will use PHP / Session 16 / Slide 13 of 24 Retrieving Cookie Value  PHP provides three ways of retrieving a cookie value:  Passing a variable as cookie name  Using $_COOKIE[]  Using $HTTP_COOKIE_VARS[] PHP / Session 16 / Slide 14 of 24 Passing... cookie name Syntax: echo $cookie_name   PHP searches all the variables present in the client computer Works only when the ‘register_globals’ is disabled in the configuration file PHP / Session 16 / Slide 15 of 24 Using $_COOKIE[]    Requires PHP 4.1 Simpler and more secured than using the $HTTP_COOKIE_VARS[] Syntax: $_COOKIE[‘$cookie_name’] PHP / Session 16 / Slide 16 of 24 Using $HTTP_COOKIE_VARS[]...     Websites use cookies to store userspecific information Cookies are stored on the Web browser’s hard disks User information and preferences are send to and from the Web browser Types of cookies:    Persistent Non-persistent Web server sends the cookie in a SetCookie header field PHP / Session 16 / Slide 22 of 24 Summary - II  PHP provides three ways of retrieving a cookie value:     Passing... Using $_COOKIE[] Using $HTTP_COOKIE_VARS[] PHP uses two functions to set a cookie, such as   setcookie() setrawcookie() PHP / Session 16 / Slide 23 of 24 Summary - III  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 Drawbacks of cookies:      Cookies cannot contain more than a certain...    Cookies cannot contain more than a certain amount of information Only a maximum of 20 cookies of a domain can be maintained A browser can maintain a maximum of 300 cookies Some users disable cookies while accessing websites Storing large number of cookie files slows down the computer PHP / Session 16 / Slide 24 of 24
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