Can't get message to display on contact form after submitting?

I have a simple contact form with a PHP email script. I also have a <div> tag that will contain a result message: successful or failure, once the message has been submitted. My problem is that I can't get the message to display within this <div> tag. I'm not real good with PHP so I'm not really sure what I'm doing wrong. Below is the PHP script which is included in my HTML as a separate file. Also, my <form> code is below to.

Code:

---

<?php
    if ($_SERVER["REQUEST_METHOD"] == "POST") {
        $message = $to = $from_email = "";
        $to = "[email protected]";

        if (empty($_POST["email"])) {
            $emailErr = "Email is required";
        }
        else {
            $from_email = $_POST["email"];

            // check if e-mail address is well-formed
            if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
                $emailErr = "Invalid email format";
            }
        }

        if (empty($_POST["message"])) {
            $emailErr = "Message is required";
        }
        else {
            $message = "\r\n";
            $message .= $_POST["message"];
        }
     
        $subject = "* * * EMAIL - Inquiry * * *";

        // compose headers
        $headers = "From: [email protected]\r\n";
        $headers .= "Reply-To: [email protected]\r\n";
        $headers .= "X-Mailer: PHP/".phpversion();

        // compose message
        $message = wordwrap($message, 70);

        // send email
        if (mail($to, $subject, $message, $headers)) {
            header('Location: http://www.something.com/#p2');   
            $_POST['user-message'] = "Thank you...your message has been sent!";
        }
        else {
            echo("Message failure!");
        }
    }
?>

---

HTML Code

Code:

---

    <div id="p2" class="boxes">
        <div id="contactMe" class="mainDiv">
            <h1>Contact Form</h1>

            <input id="user-message" name="user-message" style="background-color: #ccc">
           
            <div id="form-messages" style="width: 95%; margin: 5px auto; height: auto"></div>
            <form id="ajax-contact" action="scripts/mail3.php" method="POST">
                <label for="fullname">Full Name</label>
                <input id="name" name="name" type="text" required>

                <label for="email">E-Mail</label>
                <input id="email" name="email" type="text" required>

                <label for="message">Message</label>
                <textarea id="message" name="message" rows="3" cols="50" required></textarea>

                <button class="button" type="submit">Send E-Mail</button>
            </form>

        </div>

        <div class="backToTop"><a href="#theTop">Back to Top</a></div>
    </div>

---

Thanks,