формане отправляет input

<form id="msform" action="submit.php" method="POST"> 
  <!-- progressbar --> 
  <ul id="progressbar"> 
    <li class="active">Personal Details</li> 
    <li>Adress Details</li> 
    <li>Comment</li> 
  </ul> 
  <!-- fieldsets --> 
  <fieldset> 
    <h2 class="fs-title">Personal Details</h2> 
    <h3 class="fs-subtitle">Tell us about you</h3> 
    <input type="text" id="first_name" placeholder="Your First Name" required="" /> 
    <input type="text" id="second_name" placeholder="Your Second Name" required="" /> 
    <input type="text" id="phone" placeholder="Phone" required="" /> 
    <button type="button" name="next" class="next action-button">NEXT</button> 
  </fieldset> 
  <fieldset> 
    <h2 class="fs-title">Adress Details</h2> 
    <h3 class="fs-subtitle">Enter Your Address</h3> 
    <input type="text" id="street" placeholder="Street" required="" /> 
    <input type="text" id="building" placeholder="Building №" required="" /> 
    <input type="text" id="city" placeholder="City" required="" /> 
    <button type="button" name="previous" class="previous action-button-previous">PREVIOUS</button> 
    <button type="button" name="next" class="next action-button">NEXT</button> 
  </fieldset> 
  <fieldset> 
    <h2 class="fs-title">Comment</h2> 
    <h3 class="fs-subtitle">Fill in your comment</h3> 
    <textarea id="comment" placeholder="Comments"></textarea> 
    <button type="button" name="previous" class="previous action-button-previous">PREVIOUS</button> 
    <button type="submit" name="submit" class="submit action-button">SUMBIT</button> 
  </fieldset> 
</form>