Erro ao passar dados do form para um modal

[goncalo_gmp 0]

<form method="POST" action="<?php echo $_SERVER['PHP_SELF']?>">
            <div class="form-group row">
              <label for="title" class="col-sm-2 col-form-label">Title News:</label>
              <div class="col-sm-9">
                <input class="form-control" id="title" name="newTitle" placeholder="New´s Title">
              </div>
            </div>
            <div class="form-group row">
                  <label for="state" class="col-sm-2 col-form-labe">State:</label>
                  <div class="col-sm-9">
                    <select class="form-control" id="state" name="newState">
                      <option selected>Options</option>
                      <option value="1">Published</option>
                      <option value="2">Unpublished</option>
                    </select>
                </div>
            </div>
        </div>
          <div class="col-3 mt-5 mb-5">
            <a data-toggle="modal" data-target="#exampleModal"s><i class="material-icons">pageview</i></a>
          </div>
          <div class="col-1"></div>
          <div class="col-10 mb-5">
            <textarea id="new_text" name="newText" style="height: 400px;"></textarea>
            <input class="btn btn-outline-dark float-right mt-2" type="submit" name="save_news" value="Save" id="submit"/>
          </div>
        </form>

Ao clicar no:

Citar

<a data-toggle="modal" data-target="#exampleModal"s><i class="material-icons">pageview</i></a>

Abre meu modal:

<div class="modal fade bd-example-modal-xl" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
      <div class="modal-dialog modal-xl" role="document">
        <div class="modal-content">
          <div class="modal-header">
            <h5 class="modal-title" id="exampleModalLabel">Preview</h5>
            <button type="button" class="close" data-dismiss="modal" aria-label="Close">
              <span aria-hidden="true">&times;</span>
            </button>
          </div>
          <div class="modal-body">
            <header class="header">
              <img class="img-fluid w-100" src="./img/banner.png" alt="banner" />
              <button type="button" class="btn btn-danger m-1" href="">Back</button>
              <button type="button" class="btn btn-danger float-right m-1" href="">Login</button>
            </header>
            <div class="container-fluid">
              <div class="row mt-5 text-center">
                  <div class="col">
                      <h1><?php echo isset($_POST['newTitle']) ? $_POST['newTitle'] : '';; ?></h1>
                  </div>
              </div>
              <div class="row mt-4 text-center">
                  <div class="col">
                      <h6>Publicado pelo(a): </h6>
                      <h5><?php echo $_SESSION['UserNome']; ?></h5>
                  </div>
                  <div class="col">
                      <h6>Publicado em: </h6>
                      <h5><?php echo date('o-m-d'); ?></h5>
                  </div>
              </div>
              <div class="row mt-5 text-center">
                  <div class="col">
                      <h5><?php echo isset($_POST['newText']) ? $_POST['newText'] : '';; ?></h5>
                  </div>
              </div>
            </div>
            <div class="modal-footer">
              <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
            </div>
          </div>
        </div>
      </div>
    </div>

Porém na minha página aparece apenas 

			<div class="row mt-4 text-center">
                  <div class="col">
                      <h6>Publicado pelo(a): </h6>
                      <h5><?php echo $_SESSION['UserNome']; ?></h5>
                  </div>
                  <div class="col">
                      <h6>Publicado em: </h6>
                      <h5><?php echo date('o-m-d'); ?></h5>
                  </div>
              </div>

E se retirar a validação dos POST aparece me os erros:

Citar

Notice: Undefined index: newTitle in C:\xampp\htdocs\exercicio\novaNew.php on line 105

Notice: Undefined index: newText in C:\xampp\htdocs\exercicio\novaNew.php on line 120

Se alguém souber qual o problema que me diga por favor. Obrigado!