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