Réception d'un mail via un formulaire php

Bonjour,

J'ai mis en place sur mon site un formulaire php. Mais j'ai un soucis lorsque qqn rempli le mail et l'envoi.
Je réceptionne le mail lié, sans séparation (juste &) et les signes comme le @ (% 40) est modifié

Nom=Muriel&Prenom=Jean&email=info%40bat-design.ch

Comment est-ce que je peux éviter cela?

Je ne maîtrise pas bien le language codé

voici le code de ma page.

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

// CHANGE THE TWO LINES BELOW
$email_to = "***@***";

$email_subject = "website html form submissions";


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($_POST['nom']) ||
!isset($_POST['prenom']) ||
!isset($_POST['email']) ||
!isset($_POST['telephone']) ||
!isset($_POST['comments'])) {
died('We are sorry, but there appears to be a problem with the form you submitted.');
}

$first_name = $_POST['nom']; // required
$last_name = $_POST['prenom']; // required
$email_from = $_POST['email']; // required
$telephone = $_POST['telephone']; // not 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($string_exp,$prenom)) {
$error_message .= 'The prenom you entered does not appear to be valid.<br />';
}
if(!preg_match($string_exp,$nom)) {
$error_message .= 'The nom you entered does not appear to be valid.<br />';
}
if(strlen($comments) < 2) {
$error_message .= 'The message you entered do not appear to be valid.<br />';
}
if(strlen($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);
}

$email_message .= "Nom: ".clean_string($prenom)."\n"<br />;
$email_message .= "Prénom: ".clean_string($nom)."\n"<br />;
$email_message .= "Email: ".clean_string($email_from).\n"<br />;
$email_message .= "Tél.: ".clean_string($telephone)."\n"<br />;
$email_message .= "Message: ".clean_string($message)."\n"<br /";


// 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);
?>

<!-- place your own success html below -->

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

<?php
}
die();
?>