PHP - Cookies
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.
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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