title: Session message not displayed while other session are displayed
body: <p>I have button save and delete, when i press save button, the session message appeared, but when i press delete button, session message not appeared</p>
  
  <p>here admin_tools.php :</p>
  
  <pre><code>&lt;?php require_once 'admin_process.php'; ?&gt;
  &lt;?php 
  if (isset($_SESSION['msg'])) :?&gt;
      &lt;div class="text-center alert alert-&lt;?=$_SESSION['msg_type']?&gt;"&gt;
          &lt;a href="#" class="close" data-dismiss="alert"&gt;&amp;times;&lt;/a&gt;
      &lt;?php 
          echo $_SESSION['msg'];
          unset($_SESSION['msg']) ;
       ?&gt;
      &lt;/div&gt;
   &lt;?php endif ?&gt;
  </code></pre>
  
  <p>admin_process.php:</p>
  
  <pre><code>include "config.php"; 
  
  session_start();
  
  if (isset($_POST['save'])) {
      $nama_staff = $_POST['nama_staff'];
      $user_staff = $_POST['user_staff'];
      $pw_staff = md5($_POST['pw_staff']);
      $cabang = $_POST['cabang']; 
  
      $tambah = mysqli_query($conn,"INSERT INTO staff(nama_staff,user_staff,pw_staff,cabang) VALUES('$nama_staff','$user_staff','$pw_staff','$cabang')");
      if ($tambah) {
          mysqli_query($conn,$tambah);
          $_SESSION['msg'] = "Staff berhasil ditambahkan";
          $_SESSION['msg_type'] = "success";
          header('location:admin_tools.php');
      }
  }
  
  if (isset($_GET['delete'])) {
      $id_staff = $_GET['delete'];
      $hapus = mysqli_query($conn,"DELETE FROM staff WHERE id_staff=$id_staff");
      if ($hapus) {
          mysqli_query($conn,$hapus);
          $_SESSION['msg'] = "Staff berhasil dihapus";
          $_SESSION['msg_type'] = "danger";
          header('location:admin_tools.php');
      }
  }
  </code></pre>