HTML — код PHP не отправляет электронную почту

У меня есть эта часть кода на моей веб-странице, но она не работает должным образом.

<?php

if(isset($_POST['email'])) {$email_to = "[email protected]";

$email_subject = "Your email subject line";
function died($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['first_name']) ||

!isset($_POST['last_name']) ||

!isset($_POST['email']) ||

!isset($_POST['comments'])) {

died('We are sorry, but there appears to be a problem with the form you submitted.');

}$first_name = $_POST['first_name']; // required

$last_name = $_POST['last_name']; // required

$email_from = $_POST['email']; // required

$comments = $_POST['comments']; // required$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";

$email_message .= "Comments: ".clean_string($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);?>

Следует отправить электронное письмо на указанный адрес электронной почты.
Кроме того, я хочу, чтобы после отправки электронной почты и сообщения «Сообщение отправлено» отображались четкие поля.
Пожалуйста, помогите мне!

Ничего не происходит после добавления сообщения об ошибке.
Вот моя HTML-форма:

<form name="contactform" method="post" action="send_form_email.php">

<p>
<input type="text" name="first_name" maxlength="50" size="30" class="wpcf7-form-control wpcf7-text wpcf7-validates-as-required wpcf7-use-title-as-watermark" title="First name">
</p>
<p>
<input type="text" name="last_name" maxlength="50" size="30" class="wpcf7-form-control wpcf7-text wpcf7-validates-as-required wpcf7-use-title-as-watermark" title="Last name">
</p>
<p>
<input type="text" name="email" maxlength="80" size="30" class="wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email wpcf7-use-title-as-watermark" title="E-mail">
</p>
<p>
<textarea name="comments" maxlength="1000" cols="25" rows="6" class="wpcf7-form-control  wpcf7-textarea wpcf7-use-title-as-watermark" title="Write your message here.."></textarea>
</p>

<input type="submit" value="Submit" class="wpcf7-form-control">
<div class="wpcf7-response-output wpcf7-display-none"></div></form>