Не могу найти ошибку PHP

Итак, это моя первая попытка в PHP, поэтому исправить ее очень легко. Я пытаюсь составить форму, которую можно будет отправить и отправить на электронную почту администрации.

Я запускаю сервер с MAMP, выхожу в Интернет, заполняю форму, отправляю ее и получаю сообщение об ошибке:

We are very sorry, but there were error(s) found with the form you submitted. These errors appear below.

We are sorry, but there appears to be a problem with the form you submitted.

Please go back and fix these errors.

Полный код PHP:

<?php
if (isset($_POST['email'])) {

    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "I HAVE CORRECT EMAIL HERE 4 SURE";
    $email_subject = "eShop Contact Form";

    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }


    // validation expected data exists
    if (!isset($_POST['fname']) ||
        !isset($_POST['lname']) ||
        !isset($_POST['email']) ||
        !isset($_POST['subject'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');
    }



    $first_name = $_POST['fname']; // required
    $last_name = $_POST['lname']; // required
    $email_from = $_POST['email']; // required
    //$country = $_POST['country']; // not required
    $comments = $_POST['subject']; // required

    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';

    if (!preg_match($email_exp,$email_from)) {
        $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
    }

    $string_exp = "/^[A-Za-z .'-]+$/";

    if (!preg_match($string_exp,$first_name)) {
        $error_message .= 'The First Name you entered does not appear to be valid.<br />';
    }

    if (!preg_match($string_exp,$last_name)) {
        $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
    }

    if (strlen($comments) < 2) {
        $error_message .= 'The Comments you entered do not appear to be valid.<br />';
    }

    if (strlen($error_message) > 0) {
        died($error_message);
    }

    $email_message = "Form details below.\n\n";


    function clean_string($string) {
        $bad = array("content-type","bcc:","to:","cc:","href");
        return str_replace($bad,"",$string);
    }



    $email_message .= "First Name: ".clean_string($first_name)."\n";
    $email_message .= "Last Name: ".clean_string($last_name)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
//    $email_message .= "Country: ".clean_string($country)."\n";
    $email_message .= "Subject: ".clean_string($comments)."\n";

// create email headers
    $headers = 'From: '.$email_from."\r\n".
        'Reply-To: '.$email_from."\r\n" .
        'X-Mailer: PHP/' . phpversion();
    @mail($email_to, $email_subject, $email_message, $headers);
    ?>

    <!-- include your own success html here -->

    Thank you for contacting us. We will be in touch with you very soon.

    <?php

}
?>

Это та часть, с которой должны возникнуть проблемы:

    // validation expected data exists
    if (!isset($_POST['fname']) ||
        !isset($_POST['lname']) ||
        !isset($_POST['email']) ||
        !isset($_POST['subject'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');
    }

P.S Я скопировал сюда код из http://www.freecontactform.com/email_form.php и немного отредактировал.