$_COOKIE

The $_COOKIE variable is a special superglobal variable that stores the name and values of the cookies that were transmitted to the webserver.

The $_COOKIE variable is an associative array where the keys are the cookies names and the values are the corresponding values passed in the HTTP headers.

$_COOKIE is a superglobal : it is always available, in every scope.

Values inside $_COOKIE are always strings, or arrays.

<?php

echo $_COOKIE['username'];

?>

Documentation

Related : $_GET, $_POST, $_REQUEST, $_FILES, $_SERVER, $_ENV