Recently I want to make basic contact form. I get stucked.. I have 3 files: contact.php form.php and style.css
contact.php:
    <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <link rel="stylesheet" type="text/css" href="style.css">
  <title></title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link href="https://fonts.googleapis.com/css?family=Montserrat" rel="stylesheet">
</head>
<body>
  <section>
    <article>
      <div class="container">
        <form id="contact" action="form.php" method="post">
          <h3>Contact</h3>
          <h4>Contact us today, and get reply with in 24 hours!</h4>
          <fieldset>
            <input type="text" name="name" placeholder="Your name">
          </fieldset>
          <fieldset>
            <input type="text" name="mail" placeholder="Your Email Address">
          </fieldset>
          <fieldset>
            <input type="text" name="site" placeholder="Your Web Site starts with http://">
          </fieldset>
          <fieldset>
            <textarea name="message" placeholder="Type your Message Here...." ></textarea>
          </fieldset>
          <fieldset>
            <button type="submit" name="submit" >Submit</button>
          </fieldset>
        </form>
      </div>
    </article>
  </section>
</body>
</html>
form.php
<<?php 
if (isset($_POST['submit'])) {
  $name = $_POST['name'];
  $mail = $_POST['mail'];
  $site = $_POST['site'];
  $message = $_POST['message'];
  $mailTo = "info@example.co";
  $headers = "From: ".$mail;
  $txt = "You have received an e-mail from email".$name.".\n\n".$message;
  mail($mailTo, $name, $txt, $headers, );
  header("Location: contact.php?mailsend");
}
style.css isn't important because it was working. Whats wrong with my code? I put files on my server on my site and I get error prompt. " HTTP ERROR 500 "
Thanks for help.
 
     
    