php sms message sending script, help please, need to change the from address Options

[maxaud]

I'm piecing together a script to send text messages from one of my sites to my cell phone. I got it all work'd out all fine and It sends the message fine but the 'from address' is defined as anonymous@myserver.com when I'd like to have it as either...

1) I'd prefer to have it as the email address that the person fills out on the form that texts me

OR

2)nobody@mydomain.com

the current script is..

CODE

<?php

$to="##########@vtext.com, myemail@mydomain.com";

$sucessURL="http://www.mydomain.com/success";

$failureURL="http://www.mydomain.com/error";

$subject="sitetxt";

$msg = "Name: {$_POST['txtName']}\nPhone: {$_POST['txtNumber']}\nEmail: {$_POST['txtEmail']}\nMessage: ".nl2br($_POST['txtMessage'])."
";

$headers  = "From: {$_POST['txtEmail']}";

if(mail($to, $subject, $msg, $headers))
{
    header("Location: $sucessURL");
}
else
{
    header("Location: $failureURL");
}
?>