are like name tags;  You tell the server your name and it can give you a sticker to wear.    Then it can know who you are by referring back to that name tag.

  ex.: 

  setcookie('firstname', 'vins');

  setcookie('user_id', 'linux');

Access Cookies

To access use the $_COOKIE['value name'], along with the register_globals settings turn on in PHP.

  ex.: 

  setcookie('username', 'larry');

  $_COOKIE['username']

  the sample code below show's, how to check for an existing cookie and as follows:

  ex.: 

  IF ( !isset($_COOKIE['username'])) {

    header("location: http://".     $_SERVER['HTTP_HOST'] .     dirname($_SERVER['PHP_SELF']) .     "/index.php");

    exit();

  }

Delete or Remove a Cookie

ex.: 

  setcookie('firstname', '');

  setcookie('firstname', '', time()-300);

Cookie parameters

  syntax: 

  setcookie('name', 'value', expiration, 'path', 'domain', secure);

  ex.: 

  setcookie('name', 'value1', time()+3600);