邮件未在php中发送，给出意外令牌W

我正在使用mail（）函数发送邮件，但邮件没有发送，这会导致"意外令牌W"错误。。会出现什么问题，这是我的代码：任何人帮我解决这个问题。。。。我正在使用mail（）函数发送邮件，但邮件无法发送，这会导致"意外令牌W"错误。。会有什么问题，这是我的代码：。。。我正在使用mail（）函数发送邮件，但邮件无法发送，这会导致"意外令牌W"错误。。会出现什么问题，这是我的代码：任何人帮我解决这个问题。。。。

index.php:
<form name="" action="contact.php" method="post" class="wpcf7-form" novalidate>
                          <div style="display: none;">
                            <input type="hidden" name="_wpcf7" value="5" />
                            <input type="hidden" name="_wpcf7_version" value="4.1" />
                            <input type="hidden" name="_wpcf7_locale" value="en_US" />
                            <input type="hidden" name="_wpcf7_unit_tag" value="wpcf7-f5-p12-o1" />
                            <input type="hidden" name="_wpnonce" value="aa14dbded6" />
                          </div>
                          <div class="wpcf7-response-output wpcf7-display-none"></div>
                          <div class="row">
                            <div class="col-sm-6">
                              <div class="form-field">
                                <label for="your-name">Your Name <span>*</span></label>
                                <span class="wpcf7-form-control-wrap your-name">
                                <input type="text" name="name" value="" size="40" class="wpcf7-form-control wpcf7-text wpcf7-validates-as-required" id="your-name" aria-required="true" aria-invalid="false" />
                                </span> </div>
                              <div class="form-field">
                                <label for="your-email">Your Email <span>*</span></label>
                                <span class="wpcf7-form-control-wrap your-email">
                                <input type="email" name="email" value="" size="40" class="wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email" id="your-email" aria-required="true" aria-invalid="false" />
                                </span> </div>
                              <div class="form-field">
                                <label for="your-phone">Your Phone</label>
                                <span class="wpcf7-form-control-wrap your-phone">
                                <input type="tel" name="phone" value="" size="40" class="wpcf7-form-control wpcf7-text wpcf7-tel wpcf7-validates-as-tel" id="your-phone" aria-invalid="false" />
                                </span> </div>
                            </div>
                            <div class="col-sm-6">
                              <div class="form-field">
                                <label for="your-subject">Subject</label>
                                <span class="wpcf7-form-control-wrap your-subject">
                                <input type="text" name="subject" value="" size="40" class="wpcf7-form-control wpcf7-text" id="your-subject" aria-invalid="false" />
                                </span> </div>
                              <div class="form-field">
                                <label for="your-message">Message <span>*</span></label>
                                <span class="wpcf7-form-control-wrap your-message">
                                <textarea name="message" cols="40" rows="10" class="wpcf7-form-control wpcf7-textarea wpcf7-validates-as-required" id="your-message" aria-required="true" aria-invalid="false"></textarea>
                                </span> </div>
                              <div class="form-field">
                                <input type="submit" value="Send Message" name="submit" class="wpcf7-form-control wpcf7-submit c-button" />
                              </div>
                            </div>
                          </div>
                        </form>
contact.php:
<?php
 $to = "arundsti@gmail.com";
 $subject = 'A new Enquiry on DiamondShine';
 $name = $_REQUEST['name'];
 $email = $_REQUEST['email'];
 $phone = $_REQUEST['phone'];
 $subject=$_REQUEST['subject'];
 $date = date("Y/m/d");
 $comments = $_REQUEST['message'];

if(isset($_POST['submit'])) {

 $message = '<img src='imagedental''><br><br><br><b>Name</b>: '
 .$name.'<br><br><b>Email</b>: '
 .$email.'<br><br><b>phone</b>: '
 .$subject.'<br><br><b>Subject</b>: '
 .$phone.'<br><br><b>Messsage</b>: '
 .$comments.'<br><br><b>Date</b>: '.$date;
 // To send HTML mail, the Content-type header must be set
$headers  = 'MIME-Version: 1.0' . "'r'n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "'r'n";
// Additional headers
//$headers .= 'To: Mary <mary@example.com>, Kelly <kelly@example.com>' . "'r'n";
$headers .= 'From: DiamondShine '.$email . "'r'n";
//$headers .= 'Cc: birthdayarchive@example.com' . "'r'n";
//$headers .= 'Bcc: birthdaycheck@example.com' . "'r'n";
 $sent = mail($to, $subject, $message, $headers) ;
 if($sent)
 {
 ?>
<script type="text/javascript">
alert('Thanks for contacting Us. We will be in touch with you shortly...');
location.href = "contactus.php";
</script>
<?php
 }
 else
 {print "We encountered an error sending your mail"; }
}
?>