Working with PHP Cookies
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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>
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