Mon site ne redirige plus vers la bonne page

<?php 
if(isset($_POST['submit'])){
    $to = "info@MonSite.com"; // this is your Email address
    $from = $_POST['email']; // this is the sender's Email address
 $firstname = $_POST['firstname'];
 $lastname = $_POST['lastname'];
 $total = $_POST['subtotal'];
    $subject = "Purchase - MonSite.com";
    $subject2 = "Copy of your purchase - MonSite.com";
    $message = '1. ESSENTIAL INFORMATION TO START YOUR PROJECT'."\n"
 .'Product: '.$_POST['product']."\n"
 .'Name of project: '.$_POST['project']."\n"
 .'Quantity: '.$_POST['quantity']."\n"
 .'Size: '.$_POST['size']."\r\n\r\n"
 .'2. INFORMATION TO WRITE ON YOUR ENVELOPES '."\n"
 .'First name: '.$_POST['firstname']."\n"
 .'Last name: '.$_POST['lastname']."\n"
 .'Company name: '.$_POST['company']."\n"
 .'Profession: '.$_POST['jobposition']."\n"
 .'Phone: '.$_POST['phone']."\n"
 .'Email: '.$_POST['email']."\n"
 .'Website: '.$_POST['website']."\r\n\r\n"
 .'3. SHIPPING INFORMATION '."\n"
 .'First name: '.$_POST['firstname-shipping']."\n"
 .'Last name: '.$_POST['lastname-shipping']."\n"
 .'Address: '.$_POST['address-shipping']."\n"
 .'City: '.$_POST['city-shipping']."\n"
 .'State: '.$_POST['state-shipping']."\n"
 .'Postal code: '.$_POST['postalcode-shipping']."\n"
 .'Country: '.$_POST['country-shipping']."\r\n\r\n"
 .'4. PAYMENT INFORMATION '."\n"
 .'First name (Owner of the credit card): '.$_POST['firstname-payment']."\n"
 .'Last name (Owner of the credit card): '.$_POST['lastname-payment']."\n"
 .'Address: '.$_POST['address-payment']."\n"
 .'City: '.$_POST['city- payment']."\n"
 .'State: '.$_POST['state-payment']."\n"
 .'Postal code: '.$_POST['postalcode-payment']."\n"
 .'Country: '.$_POST['country-payment']."\n"
 .'Method of payment: '.$_POST['creditcardtype']."\n"
 .'Credit card number: '.$_POST['creditcard']."\n"
 .'Expiry month: '.$_POST['month']."\n"
 .'Expiry year: '.$_POST['year']."\n"
 .'CVV: '.$_POST['cvv'];
 $message2 = '1. ESSENTIAL INFORMATION TO START YOUR PROJECT'."\n"
 .'Name of project: '.$_POST['project']."\n"
 .'Quantity: '.$_POST['quantity']."\n"
 .'Size: '.$_POST['size']."\r\n\r\n"
 .'2. INFORMATION TO WRITE ON YOUR ENVELOPES '."\n"
 .'First name: '.$_POST['firstname']."\n"
 .'Last name: '.$_POST['lastname']."\n"
 .'Company name: '.$_POST['company']."\n"
 .'Profession: '.$_POST['jobposition']."\n"
 .'Phone: '.$_POST['phone']."\n"
 .'Email: '.$_POST['email']."\n"
 .'Website: '.$_POST['website']."\r\n\r\n"
 .'3. SHIPPING INFORMATION '."\n"
 .'First name: '.$_POST['firstname-shipping']."\n"
 .'Last name: '.$_POST['lastname-shipping']."\n"
 .'Address: '.$_POST['address-shipping']."\n"
 .'City: '.$_POST['city-shipping']."\n"
 .'State: '.$_POST['state-shipping']."\n"
 .'Postal code: '.$_POST['postalcode-shipping']."\n"
 .'Country: '.$_POST['country-shipping']."\r\n\r\n"
 .'4. PAYMENT INFORMATION '."\n"
 .'First name (Owner of the credit card): '.$_POST['firstname-payment']."\n"
 .'Last name (Owner of the credit card): '.$_POST['lastname-payment']."\n"
 .'Address: '.$_POST['address-payment']."\n"
 .'City: '.$_POST['city- payment']."\n"
 .'State: '.$_POST['state-payment']."\n"
 .'Postal code: '.$_POST['postalcode-payment']."\n"
 .'Country: '.$_POST['country-payment']."\n"
 .'Your Method of payment: '.$_POST['creditcardtype']."\n";
 $message3 = "Dear " . $name . ",\r\n\r\nThank you for choosing MonSite.com.\r\n\r\nThis email confirms that your message has been received and you should get a reply as soon as possible.\r\n\r\nHere is the copy of your message : \r\n" . $message2 . "\r\n\r\n\r\n"
 .'We appreciate your interest on our website.'."\r\n\r\n"
 .'Customer Service Team'."\r\n"
 .'MonSite.com';
 $headers = "From:" . $from;
    $headers2 = "From:" . $to;
    mail($to, $subject, $message, $headers);
    mail($from, $subject2, $message3, $headers2); // sends a copy of the message to the sender
 header('location: thanks-purchase.html');
}
exit();
?>