PHP変数をブートストラップモーダルに渡す

これをループの中に入れてください

<button type="button" class="btn btn-success" data-toggle="modal" data-target="#message<?php echo $row['id'];?>">Message</button>

<div id="message<?php echo $row['id'];?>" class="modal fade" role="dialog">
  <div class="modal-dialog">

    <!-- Modal content-->
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal">&times;</button>
        <h4 class="modal-title">Modal Header</h4>
      </div>
      <div class="modal-body">
        <p>Some text in the modal.</p>
        <?php echo $row['id'];?>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
      </div>
    </div>

  </div>
</div>