PHP联系表单成功发送电子邮件但无法重定向到感谢页面

Question

I'm a beginner when it comes to PHP.

This is a 'contact us' form where users can send their questions. Currently, it's successful in sending submitted questions directly to our email. However, it failed to redirect to a thank you page after the submission. I sincerely hope that someone could help me. I'm lost. The codes are below. Thank you in advance.

<?php

// Define some constants
define( "RECIPIENT_NAME", "Choice Baby Enquiry" );
define( "RECIPIENT_EMAIL", "[e-mail]" );

// Read the form values
$success = false;
$senderName = isset( $_POST['name'] ) ? preg_replace( "/[^\.\-\' a-zA-Z0-9]/", "", $_POST['name'] ) : "";
$senderEmail = isset( $_POST['email'] ) ? preg_replace( "/[^\.\-\_\@a-zA-Z0-9]/", "", $_POST['email'] ) : "";
$subject = isset( $_POST['subject'] ) ? preg_replace( "/[^\.\-\' a-zA-Z0-9]/", "", $_POST['subject'] ) : "Enquiry";
$message = isset( $_POST['message'] ) ? preg_replace( "/(From:|To:|BCC:|CC:|Subject:|Content-Type:)/", "", $_POST['message'] ) : "";

// If all values exist, send the email
if ( $senderName && $senderEmail && $message ) {
  $recipient = RECIPIENT_NAME . " <" . RECIPIENT_EMAIL . ">";
  $headers = "From: " . $senderName . " <" . $senderEmail . ">";
  $success = mail( $recipient, $subject, $message, $headers );
}

if ( mail( $recipient, $subject, $message, $headers )) {
    header ("Location: thanks.html");
    exit ();
}

?>

----EDIT----

Here is the HTML :

<section class="contact_us_container">
            <div class="container">
                <div class="row">
                    <div class="col-lg-12 col-md-12 col-sm-12 col-xs-12" style="text-align:center;"> <!-- section title -->
                        <h2>Get In Touch With Us</h2>
                        <p>Type your question here and we will get back to you as soon as possible.</p>
                    </div> <!-- End section title -->
                    <div class="col-lg-8 col-md-8 col-sm-12 col-xs-12 form_holder"> <!-- form holder -->
                        <form action="includes/sendemail.php" class="contact-form">
                            <input class="form-control name" type="text" name="name" placeholder="Your Name">
                            <input class="form-control email" type="email" name="email" placeholder="Your Email">
                            <input class="form-control" type="text" name="subject" placeholder="Subject">
                            <textarea name="message" placeholder="Your Message"></textarea>
                            <button type="submit" class="submit">submit now<i class="fa fa-arrow-circle-right"></i></button>
                        </form> <!-- End form holder -->
                    </div>
                    <div class="col-lg-4 col-md-4 col-sm-12 col-xs-12 pull-right address">
                        <address>
                            <div class="icon_holder float_left"><span class="icon icon-Pointer"></span></div>
                            <div class="address_holder float_left">M2-19-03,<br>8trium Tower, Jalan Cempaka SD 12/5,<br>Bandar Sri Damansara,52000 KL</div>
                        </address>
                        <address class="clear_fix">
                            <div class="icon_holder float_left"><span class="icon icon-Plaine"></span></div>
                            <div class="address_holder float_left">[e-mail]</div>
                        </address>
                        <address class="clear_fix">
                            <div class="icon_holder float_left"><span class="icon icon-Phone2"></span></div>
                            <div class="address_holder float_left">+ 603 6735 5374</div>
                        </address>
                    </div>
                </div>
            </div>
        </section>

Answer 1

HTML Code :

<form action="includes/sendemail.php" class="contact-form" method="post">
    <input class="form-control name" type="text" name="name" placeholder="Your Name">
    <input class="form-control email" type="email" name="email" placeholder="Your Email">
    <input class="form-control" type="text" name="subject" placeholder="Subject">
    <textarea name="message" placeholder="Your Message"></textarea>
    <button type="submit" class="submit" name="btnSubmit">submit now<i class="fa fa-arrow-circle-right"></i></button>
</form>

PHP Code : includes/sendemail.php

<?php
if(isset($_POST["btnSubmit"]))
{
    // Define some constants
    define( "RECIPIENT_NAME", "Choice Baby Enquiry" );
    define( "RECIPIENT_EMAIL", "[e-mail]" );

    // Read the form values
    $success = false;
    $senderName = isset( $_POST['name'] ) ? preg_replace( "/[^\.\-\' a-zA-Z0-9]/", "", $_POST['name'] ) : "";
    $senderEmail = isset( $_POST['email'] ) ? preg_replace( "/[^\.\-\_\@a-zA-Z0-9]/", "", $_POST['email'] ) : "";
    $subject = isset( $_POST['subject'] ) ? preg_replace( "/[^\.\-\' a-zA-Z0-9]/", "", $_POST['subject'] ) : "Enquiry";
    $message = isset( $_POST['message'] ) ? preg_replace( "/(From:|To:|BCC:|CC:|Subject:|Content-Type:)/", "", $_POST['message'] ) : "";

    // If all values exist, send the email
    if ( $senderName && $senderEmail && $message ) {
      $recipient = RECIPIENT_NAME . " <" . RECIPIENT_EMAIL . ">";
      $headers = "From: " . $senderName . " <" . $senderEmail . ">";
      $success = mail( $recipient, $subject, $message, $headers );
    }

    if ( mail( $recipient, $subject, $message, $headers ))
    {
        header ("Location: thanks.html");
        exit ();
    }
}
?>

Replace with this code..