提交页面的联系表单后，只需刷新

Question

当我提交此联系表单时，所有发生的事情都是页面刷新。没有邮件发送也没有错误消息。我是从本地主机发送的，但我已经知道它有效，因为我发送的电子邮件具有相同的联系表单但是当我添加验证时它不再有效。我对它为什么要刷新感到非常困惑。

HTML

<section id="contact">
            <h1 class="section-header">Contact Us Directly</h1>
            <h4 class="text-center">Have any quesitons not answered in the <span><a href="questions.php">Questions Page</a></span>.</h4>
            <form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="POST">
                <label for="fname">First Name</label>
                <input type="text" id="fname" name="firstname" value="<?php $firstname ?>" placeholder="Your name.." tabindex="1" autofocus> <span class="error"><?php $firstname_error ?></span>
                <label for="lname">Last Name</label>
                <input type="text" id="lname" name="lastname" value="<?php $lastname ?>" placeholder="Your last name.." tabindex="2"> <span class="error"><?php $lastname_error ?></span>
                <label for="email">Email</label>
                <input type="text" id="email" name="email" value="<?php $email ?>" placeholder="Your email.." tabindex="3"> <span class="error"><?php $email_error ?></span>
                <label for="message">Message</label>
                <textarea id="subject" name="message" value="<?php $message ?>" placeholder="Write something.." style="height:200px" tabindex="4"> </textarea> <span class="error"><?php $message_error ?></span>
                <input type="submit" value="Submit" tabindex="5"> <span class="success"><?php $success ?></span> </form>
        </section>

PHP

 <?php

  $firstname_error = $lastname_error = $email_error = $message_error = "";
  $firstname = $lastname = $email = $message = $success = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {
  if (empty($_POST["firstname"])) {
    $firstname_error = "First name is required";
  } else {
    $firstname = test_input($_POST["firstname"]);
    // check if name only contains letters and whitespace
    if (!preg_match("/^[a-zA-Z ]*$/", $firstname)) {
        $firstname_error = "Only letters and white space allowed";
    }
}

if (empty($_POST["lastname"])) {
    $lastname_error = "Last name is required";
} else {
    $lastname = test_input($_POST["lastname"]);
    // check if name only contains letters and whitespace
    if (!preg_match("/^[a-zA-Z ]*$/",$lastname)) {
        $lastname_error = "Only letters and white space allowed";
    }
}

if (empty($_POST["email"])) {
    $email_error = "Email is required";
} else {
    $email = test_input($_POST["email"]);
    // check if e-mail address is well-formed
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $email_error = "Invalid email format";
    }
}

if (empty($_POST["message"])) {
    $message_error = "Message is required";
} else {
    $message = test_input($_POST["message"]);
}


if ($firstname_error == '' and $lastname_error == '' and $email_error == '' and $message_error == '' ){
    $Body = "";
    $Body .= "Firstname: ";
    $Body .= $firstname;
    $Body .= "\n";
    $Body .= "Lastname: ";
    $Body .= $lastname;
    $Body .= "\n";
    $Body .= "Email: ";
    $Body .= $email;
    $Body .= "\n";
    $Body .= "Message: ";
    $Body .= $message;
    $Body .= "\n";

    $EmailFrom = localhost;
    $EmailTo = "testrepairmail69@gmail.com";
    $Subject = "New Order From tabletscreenfixer.com";
    $success = mail($EmailTo, $Subject, $Body, "From: <$email>");
    if ($success){
        print "<meta http-equiv=\"refresh\" content=\"0;URL=contactthanks.php\">";
        $firstname = $lastname = $email = $message = '';
    }else{
        print "<meta http-equiv=\"refresh\" content=\"0;URL=contactfail.php\">";
        $firstname = $lastname = $email = $message = '';
    } 
 }
 }
    function test_input($data) {
       $data = trim($data);
       $data = stripslashes($data);
       $data = htmlspecialchars($data);
       return $data;
    }

 ?>