Day 10 - Let's Eat Cookie - Become PHP Expert in 30 days

[melbin]

http://php.flashwebhost.com/melbin/set_cookie.php

<?php

if (isset($_COOKIE['VisitorName'])) {
    echo 'Hi ' . $_COOKIE['VisitorName'];
    exit;
}

if (isset($_POST['VisitorName']) && strlen($_POST['VisitorName']) > 3) {
    setcookie('VisitorName', $_POST['VisitorName'], time() + (86400 * 7)); // Remember 1 week
    echo 'Cookie Set. Close the browser. Revisit this page, I will remember your name for 1 week';
} else {

    echo '
        What is your name ?
        <form method="post" action="">
        <input type="text" name="VisitorName">
        <button type="submit" name="Submit">Remember Me</button>
        </form>
    ';
}

I am getting the following warning message

Warning: Cannot modify header information - headers already sent by (output started at /home/fwhphp/public_html/melbin/set_cookie.php:1) in /home/fwhphp/public_html/melbin/set_cookie.php on line 9

Why ??