Simple PHP E-mail Confirmation

[Abbster22]

I have a form that people are filling out to unsubscribe to a newsletter and I have the form figured out. But whenever I fill out the form and press the button to send the information to a specific e-mail, the page but the header on the web page is blank (or none of the echoing from the PHP shows up).

Here is the form code:

<form method="post" action="unsubscribe_submit.php">
            <label for="firstname">First name:</label>
    <input type="text" id="firstname" name="firstname" /><br />
    <label for="lastname">Last name:</label>
    <input type="text" id="lastname" name="lastname" /><br />
    <label for="email">E-mail Address:</label>
    <input type="text" id="email" name="email" /><br />
    <input type="submit" value="Unsubscribe" name="submit" />
    </form>

Here is the php code:

<?php
			$name = $_POST['firstname'] . ' ' . $_POST['lastname'];
			$email = $_POST['email'];
			
			$to = "a.shipley22@gmail.com";
			$subject = "User Unsubscribing From Newsletter";
			$msg = "$name would like to unsubscribe from the electronic newsletter.  $name's e-mail address is $email.";
			if(mail($to, $subject, $msg, 'From: ' . $email)) {
				echo("We are sorry to hear you are unsubscribing from our newsletter.\nWe hope that you continue to support SmileHealthy."); }
				else { echo("Message unsuccessfully sent."); }
			?>

Any help is appreciated.