表单提交后的令牌会话为空

Question

如果用户请求（GET）联系站点，我将设置会话令牌。提交表单后，我将令牌与表单中的令牌进行比较，但是我设置的令牌为空。这是我的代码：

<?php

  session_start();

  function debug_to_console($data)
  {
      $output = $data;
      if (is_array($output)) {
          $output = implode(',', $output);
      }

      echo "<script>console.log( 'Debug Objects: " . $output . "' );</script>";
  }

  //response generation function
  $response = "";


  function valid_spam_prevention($rob_email, $rob_website, $rob_phone)
  {
      debug_to_console($_POST['token']);
      debug_to_console($_SESSION['royce']); // always empty
      /* Please check me what is wrong with me

      if ($_SESSION['token'] !== $_POST['token']) {
          debug_to_console("Token false");
          return false;
      }
      */
      if (empty($rob_email) && empty($rob_website) && empty($rob_phone)) {
          return true;
      }

      return false;
  }

  //user posted variables
  $name = $_POST['message_name'];
  $email = $_POST['message_email'];
  $message = $_POST['message_text'];

  // rob posted variables
  $rob_email = $_POST['email'];
  $rob_website = $_POST['website'];
  $rob_phone = $_POST['phone'];

    if ($_SERVER['REQUEST_METHOD'] == 'POST') {
        if (valid_spam_prevention($rob_email, $rob_website, $rob_phone)) {
            unset($_SESSION['royce']);
            // validate email and send etc
        } elseif ($_POST['submitted']) {
            // missing content error
        }
    } else {
        // user request site with GET
        $token = bin2hex(random_bytes(32));
        $_SESSION['royce'] = $token;
    }
?> 

表单代码：

<form action="/contact" method="post">
                  <input type="hidden" name="token" value="<?php echo (isset($_SESSION['token'])) ? $_SESSION['token'] : ''?>">
                  <div>
                    <label for="message_name">Name</label>
                    <input id="message_name" name="message_name" type="text" value="<?php echo esc_attr($_POST['message_name']); ?>">
                  </div>
                  <div>
                    <label for="message_email">Mail</label>
                    <input id="message_email" name="message_email" type="email" value="<?php echo esc_attr($_POST['message_email']); ?>">
                  </div>
                  <div>
                    <textarea id="message_text" name="message_text"><?php echo esc_textarea($_POST['message_text']); ?></textarea>
                  </div>

                  <input id="email" name="email" type="email" autocomplete="false">
                  <input id="website" name="website" type="text" autocomplete="false">
                  <input id="phone" name="phone" type="text" autocomplete="false">

                  <button type="submit">Send</button>
                </form>

对此我有何建议？

PHP版本：7.0.30