500内部服务器错误

Question

当我尝试测试“联系我们”表单时，我收到此错误。填写表格并点击发送后我收到此错误

http://i62.tinypic.com/axz3ir.png

然而，这是我的代码：HTML

<!------contact------------->
    <div class="contact" id="contact">
        <h3 class="heading">Contact</h3>
        <p class="desc">we would really love to hear from you</p>
        <h6> </h6>
        <div class="contact-bg">
                <div class="tool_tip">
                    <a href="#"><img src="web/images/logo1.png"/></a>
                </div>

                <div class="wrap">
                    <div class="form">
                    <div class="contact-form">
                            <form method="post" action="contact-post.html">
                                         <div>
                                            <span><label>Name</label></span>
                                            <span><input name="userName" type="text" class="textbox"></span>
                                        </div>
                                        <div>
                                            <span><label>E-Mail</label></span>
                                            <span><input name="userEmail" type="text" class="textbox"></span>
                                        </div>
                                        <div>
                                            <span><label>Subject</label></span>
                                            <span><input name="userPhone" type="text" class="textbox"></span>
                                        </div>
                                        <div>
                                            <span><label>Message</label></span>
                                            <span><textarea name="userMsg"> </textarea></span>
                                        </div>
                                       <div>
                                            <span><input type="submit" value="Send"></span>
                                      </div>
                                </form>         
                    </div>
                    <div class="address">
                        <h3 class="heading">Contactinfo</h3>
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt.</p>
                        <p>quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
                        <div class="c_grids">
                            <a class=" icon pointor" href="#"> </a>
                            <p>Lorem ipsum dolor 123</p>
                            <p>1000 Lorem ipsum</p>
                            <div class="clear"> </div>
                        </div>
                        <div class="c_grids">
                            <a class=" icon contact-img" href="#"> </a>
                            <p>Lorem ipsum dolor 123</p>
                            <p>1000 Lorem ipsum</p>
                            <div class="clear"> </div>
                        </div>
                        <div class="c_grids">
                            <a class=" icon website" href="#"> </a>
                            <p>Lorem ipsum dolor 123</p>
                            <p>1000 Lorem ipsum</p>
                            <div class="clear"> </div>
                        </div>
                    </div>

                <div class="clear"> </div>
                </div>
            </div>
        </div>
    </div>
    <!------end-contact--------->

这是我的PHP代码：

 <?php 

    include "app/config.php";
    include "app/detect.php";

    if ($page_name=='') {
        include $browser_t.'/index.html';
        }
    elseif ($page_name=='index.html') {
        include $browser_t.'/index.html';
        }
    elseif ($page_name=='contact-post.html') {
        include 'app/contact.php';
        }
    else
        {
            include $browser_t.'/404.html';
        }

    ?>

并将其指向此代码：

<?php           
            $userName=$_REQUEST['userName'];
            $userEmail=$_REQUEST['userEmail'];
            //$userPhone=$_REQUEST['userPhone'];
            $userMsg=$_REQUEST['userMsg'];
            $subject = "Message from ".$userName; 
            $message = '<html><head><title>'.$subject.'</title></head><body><table><tr><td>Email id :  </td><td> '.$userEmail.'</td></tr>
<tr><td>Phone No : </td><td> '.$userName.'</td></tr><tr><td>Says : </td><td> '.$userMsg.'</td>
</tr></table></body></html>';
            //$message = "Email id :  ".$userEmail. "\r\nPhone No : ".$userPhone."\r\nName : ".$userName."\r\nSays : ".$userMsg;
            $to= "Test@Gmail.com" ;
            $headers = "From: " . strip_tags($userEmail) . "\r\n";
            $headers .= "Reply-To: ". strip_tags($userEmail) . "\r\n";
            //$headers .= "CC: susan@example.com\r\n";
            $headers .= "MIME-Version: 1.0\r\n";
            $headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
            if(!mail($to, $subject, $message, $headers)){
             $mail_status='no';
                header("Location: index.html");
            exit();
          }else{
              $mail_status='yes';
            header("Location: index.html");
            exit();

         } ?>