Showing posts with label PHP COOKIES. Show all posts
Showing posts with label PHP COOKIES. Show all posts

Thursday, 4 September 2014

PHP: COOKIES in PHP

Cookies are text files stored on the client computer and they are kept of use tracking purpose. PHP transparently supports HTTP cookies.
There are three steps involved in identifying returning users:
  • Server script sends a set of cookies to the browser. For example name, age, or identification number etc.
  • Browser stores this information on local machine for future use.
  • When next time browser sends any request to web server then it sends those cookies information to the server and server uses that information to identify the user.
This chapter will teach you how to set cookies, how to access them and how to delete them.

The Anatomy of a Cookie:

Cookies are usually set in an HTTP header (although JavaScript can also set a cookie directly on a browser). A PHP script that sets a cookie might send headers that look something like this:
HTTP/1.1 200 OK
Date: Fri, 04 Feb 2000 21:03:38 GMT
Server: Apache/1.3.9 (UNIX) PHP/4.0b3
Set-Cookie: name=xyz; expires=Friday, 04-Feb-07 22:03:38 GMT; 
                 path=/; domain=tutorialspoint.com
Connection: close
Content-Type: text/html
As you can see, the Set-Cookie header contains a name value pair, a GMT date, a path and a domain. The name and value will be URL encoded. The expires field is an instruction to the browser to "forget" the cookie after the given time and date.
If the browser is configured to store cookies, it will then keep this information until the expiry date. If the user points the browser at any page that matches the path and domain of the cookie, it will resend the cookie to the server.The browser's headers might look something like this:
GET / HTTP/1.0
Connection: Keep-Alive
User-Agent: Mozilla/4.6 (X11; I; Linux 2.2.6-15apmac ppc)
Host: zink.demon.co.uk:1126
Accept: image/gif, */*
Accept-Encoding: gzip
Accept-Language: en
Accept-Charset: iso-8859-1,*,utf-8
Cookie: name=xyz
A PHP script will then have access to the cookie in the environmental variables $_COOKIE or $HTTP_COOKIE_VARS[] which holds all cookie names and values. Above cookie can be accessed using $HTTP_COOKIE_VARS["name"].

Setting Cookies with PHP:

PHP provided setcookie() function to set a cookie. This function requires upto six arguments and should be called before <html> tag. For each cookie this function has to be called separately.
setcookie(name, value, expire, path, domain, security);
Here is the detail of all the arguments:
  • Name - This sets the name of the cookie and is stored in an environment variable called HTTP_COOKIE_VARS. This variable is used while accessing cookies.
  • Value -This sets the value of the named variable and is the content that you actually want to store.
  • Expiry - This specify a future time in seconds since 00:00:00 GMT on 1st Jan 1970. After this time cookie will become inaccessible. If this parameter is not set then cookie will automatically expire when the Web Browser is closed.
  • Path -This specifies the directories for which the cookie is valid. A single forward slash character permits the cookie to be valid for all directories.
  • Domain - This can be used to specify the domain name in very large domains and must contain at least two periods to be valid. All cookies are only valid for the host and domain which created them.
  • Security - This can be set to 1 to specify that the cookie should only be sent by secure transmission using HTTPS otherwise set to 0 which mean cookie can be sent by regular HTTP.
Following example will create two cookies name and age these cookies will be expired after one hour.
<?php
   setcookie("name", "John Watkin", time()+3600, "/","", 0);
   setcookie("age", "36", time()+3600, "/", "",  0);
?>
<html>
<head>
<title>Setting Cookies with PHP</title>
</head>
<body>
<?php echo "Set Cookies"?>
</body>
</html>

Accessing Cookies with PHP

PHP provides many ways to access cookies.Simplest way is to use either $_COOKIE or $HTTP_COOKIE_VARS variables. Following example will access all the cookies set in above example.
<html>
<head>
<title>Accessing Cookies with PHP</title>
</head>
<body>
<?php
echo $_COOKIE["name"]. "<br />";
/* is equivalent to */
echo $HTTP_COOKIE_VARS["name"]. "<br />";

echo $_COOKIE["age"] . "<br />";
/* is equivalent to */
echo $HTTP_COOKIE_VARS["name"] . "<br />";
?>
</body>
</html>
You can use isset() function to check if a cookie is set or not.
<html>
<head>
<title>Accessing Cookies with PHP</title>
</head>
<body>
<?php
  if( isset($_COOKIE["name"]))
    echo "Welcome " . $_COOKIE["name"] . "<br />";
  else
    echo "Sorry... Not recognized" . "<br />";
?>
</body>
</html>

Deleting Cookie with PHP

Officially, to delete a cookie you should call setcookie() with the name argument only but this does not always work well, however, and should not be relied on.
It is safest to set the cookie with a date that has already expired:
<?php
  setcookie( "name", "", time()- 60, "/","", 0);
  setcookie( "age", "", time()- 60, "/","", 0);
?>
<html>
<head>
<title>Deleting Cookies with PHP</title>
</head>
<body>
<?php echo "Deleted Cookies" ?>
</body>
</html>

How do you delete cookies in PHP?

The interesting thing about deleting a cookie in PHP is the fact that you must use the same PHP function that you would use to create the cookie – and that is the setcookie function.

Deleting cookies using the setcookie function in PHP

The setcookie() function can actually accept up to six arguments, but only one argument is actually required — and that is the cookie name. If you use the setcookie function, and just pass a cookie name without a value, then it will have the same effect as deleting the existing cookie with the same exact name. For example, to create a cookie called first_name, you use this line: 
   setcookie('first_name', 'Robert');
And to delete the first_name cookie, you would do this:

Example of deleting a cookie in PHP:

setcookie('first_name');
But, as an extra safety measure, you should also set the expiration time to a time in the past – as you can see below where we pass in “time() – 300″ for the expiration date. This is the way we recommend that you delete the cookie in PHP:

Recommended way to delete a cookie in PHP:

setcookie('first_name', '', time()-300);

Parameters that must be set when deleting a cookie

When you delete a cookie, you should always use the same exact parameters that were used to create the cookie in the first place. For example, If you set the domain and path when you created the cookie, then you should use those parameters again when deleting the cookie.

Other interesting facts about deleting cookies in PHP

When deleting a cookie, that deletion does not actually take effect until the page has been reloaded or another page has been accessed. This means that a cookie will still be available to a given page even after that page has deleted that cookie – but once the page is reloaded or another page is accessed in that browser window the cookie will be deleted.

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