<?php
    $cookie_var = "username";
    $cookie_val = "admin";
    setcookie($cookie_var, $cookie_val, time() - 3600); //-3600 means it has expired
?>

<html>
<body>
<?php
    if(!isset($_COOKIE[$cookie_var])) 
    {
        echo "Cookie is deleted";
    }
?>
</body>
</html>