Cookies and Session in PHP


Cookies and Session in PHP


What is a Cookie?
A cookie is often used to identify a user. A cookie is a small file that the server embeds on
the user's computer. Each time the same computer requests a page with a browser, it will
send the cookie too. With PHP, you can both create and retrieve cookie values.

Create Cookies With PHP

A cookie is created with the setcookie() function.

Syntax:
setcookie(name, value, expire, path, domain, secure, httponly);

Only the name parameter is required. All other parameters are optional.

PHP Create/Retrieve a Cookie

The following example creates a cookie named "user" with the value "John Doe". The cookie
will expire after 30 days (86400 * 30). The "/" means that the cookie is available in entire
website (otherwise, select the directory you prefer).
We then retrieve the value of the cookie "user" (using the global variable $_COOKIE). We
also use the isset() function to find out if the cookie is set:
Example:

<?php
$cookie_name = "user";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); // 86400 = 1 day
?>
<html>
<body>
<?php
if(!isset($_COOKIE[$cookie_name])) {
echo "Cookie named '" . $cookie_name . "' is not set!";
} else {
echo "Cookie '" . $cookie_name . "' is set!<br>";
echo "Value is: " . $_COOKIE[$cookie_name];
}
?>

</body>
</html>

Output:
Cookie 'user' is set!
Value is: John Doe
Note: You might have to reload the page to see the value of the cookie.
Delete a Cookie
To delete a cookie, use the setcookie() function with an expiration date in the past:
Example

<?php
// set the expiration date to one hour ago
setcookie("user", "", time() - 3600);
?>
<html>
<body>
<?php
echo "Cookie 'user' is deleted.";
?>
</body>
</html>

Output:
Cookie 'user' is deleted.

Check if Cookies are Enabled
The following example creates a small script that checks whether cookies are enabled. First,
try to create a test cookie with the setcookie() function, then count the $_COOKIE array
variable:
Example:

<html>
<?php
setcookie("test_cookie", "test", time() + 3600, '/');
?>
<html>
<body>
<?php
if(count($_COOKIE) > 0) {
echo "Cookies are enabled.";
} else {
echo "Cookies are disabled.";
}
?>
</body>
</html>

Output: Cookies are enabled.
What is a PHP Session?
When you work with an application, you open it, do some changes, and then you close it.
This is much like a Session. The computer knows who you are. It knows when you start the
application and when you end. But on the internet there is one problem: the web server
does not know who you are or what you do, because the HTTP address doesn't maintain
state.

Session variables solve this problem by storing user information to be used across multiple
pages (e.g. username, favorite color, etc). By default, session variables last until the user
closes the browser.

So; Session variables hold information about one single user, and are available to all pages
in one application.

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