Почему не выводятся значения формы?

<form action="php/data_processing.php" method="POST" class="form">
      <div class="input-wrapper">
        <label for="full_name"></label>
        <input class="item-input full_name" id="full_name" placeholder="ФИО">
      </div>
      <div class="input-wrapper">
        <label for="phone"></label>
        <input type="tel" class="item-input phone" id="phone" placeholder="Номер телефона">
      </div>
      <div class="input-wrapper">
        <label for="street"></label>
        <input class="item-input street" id="street" placeholder="Название улицы">
      </div>
      <div class="input-wrapper">
          <label for="house_number"></label>
          <input class="item-input house_number" id="house_number" placeholder="Номер дома">
        </div>
      <div class="sumbit-wrapper">
        <label for="submit"></label>
        <input type="submit" class="btn-submit" id="submit" disabled>
      </div>
    </form>

<?php
/* Передача данных в PHP */

if($_SERVER['REQUEST_METHOD'] == 'POST') { // была ли отправлены форма 
  $full_name = $_POST['full_name'];
  $phone = $_POST['phone'] ;
  $street = $_POST['street'];
  $house_number = $_POST['house_number'];

  echo $full_name, $phone,  $street , $house_number;
  }
?>