[Easy Problem]

[code]
<form method="post" action="mail.php?send=1">
<input type="text" name="subject" value="Subject goes here" /><br />
<textarea name="body">Message goes here</textarea><br />
<input type="submit" value="Send" />
</form>
<pre>
<?PHP
    if($_GET['send'] == 1)
    {
        $from = 'from@address.here';                
        $sendto = array(    'address@one.com',
                            'address@two.com',
                            'address@three.com');    
        foreach($sendto as $val)
        {
            echo 'Sending message to: '.$val.' <br />';
            mail($val, $_POST['subject'], $_POST['body'], 'From: '.$from);
        }
    }
?>
</pre>
[/code]

i'm working on a project for school and I can't get this damn thing to work, I want to send 1 e-mail to like 150 people, but this is all i could get and it doesn't work - could someone please explain it to me or help me fix it?