We use cookie to identify the identity of a user and make sure that the user is an authentic user when user traverses through different pages of an application or a website. Basically a cookie is a file in text format that is embedded by the server on the user's computer. Every time the server sends a response it also sends the cookie along with the response.There are some php functions that help us to create and retrieve cookie values.

1- Creating Cookie : We create a cookie with the help of a php function setcookie().

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

In the setcookie funciton all the parameters are optional except name.
 

Example (creating cookie):

<?php

$cookiename = "democookie"; // here a name is assigned to the variable

$cookievalue = "Testing the demo cookie"; // here a value is assigned to the variable

setcookie($cookiename, $cookievalue, time() + (86400 *10), "/"); // As 86400 seconds = 1 day

?>

Now let us retrieve the cookie name and value:
 

Example (retrieving cookie):

<?php

echo "Cookie name is :'" .$_COOKIE[$cookiename] ;

echo <br>;

echo "Cookie value is :'" . $_COOKIE[$cookievalue] ;

}

?>

3- Modifying a cookie : To modify the cookie we again use the same function setcookie() and change the value of the variable $cookiename and $cookievalue

4- Deleting a cookie : For deleting a cookie we againg use the function setcookie and set the expiry date to 3 hour ago or as per the requirement.

For example:

<?php

// setting the cookie expiry date to 3 hour ago

setcookie("user", "", time() - 10800);

?>