Codeigniter: status change by dynamic dropdown using ajax

Question

I am getting the list of users, the last column in my table is for user's status, default is new and admin can change the status new to done, I am new in Codeigniter so not getting an idea what went wrong in my code.

My view:

              <thead>
                    <th>Sr.no</th>
                    <th>Hospital Name</th>
                    <th>Blood type</th>
                    <th>Status</th>
              </thead>
              <tbody>
                    <?php if(count($all_blood>0))
                    {
                          $i=0;
                          foreach ($all_blood as $user) 
                          {
                                $i++;
                                ?>
                                <tr>
                                      <td><?php echo $i ?></td>
                                      <td><?php echo $user->h_name ?></td>
                                      <td><?php echo $user->btype?></td>
                                      <td>
                                      <select id="statusChange[<?= $user->req_id ?>]" <?php if ($user->status == 1) :?> disabled <?php endif;?> class="check">
                                            <option value="0" <?php if (0 == $user->status) : ?> selected<?php endif; ?>>New</option>
                                            <option value="1" <?php if (1 == $user->status) : ?> selected<?php endif; ?>>Done</option>
                                      </select>
                                      </td>
                                      <td>
                                      <?php $id = $user->req_id;?>
                                      <a  href="<?php echo site_url("users/delete/$id")?>" class="delete">Delete</a>
                                      </td>
                                </tr>
                                <script>
                                $(window).on('load', function() {
                                      $("#statusChange[<?= $user->req_id ?>]").on('change',function() 
                                      {
                                            console.log("change");
                                            $.ajax({
                                            type:'POST',
                                            data:{id:"<?= $user->req_id?>"},
                                            url:'<?php echo base_url("getData/change_status"); ?>',
                                                  success:function(data){
                                                        console.log(data);
                                                  }
                                            });
                                            event.preventDefault();
                                      });
                                });
                                </script>
                  <?php   }
                    }?>
              </tbody>

now I try to put ajax out of foreach loop, but there is an issue that I am not getting req_id for my ajax, which I need to send to controller, here is another issue, I am trying to use dynamic class or id so it will only which admin will select, but it is not working

if I change my dropdown's id to simple "statusChange" the function .on('change') works very well, but if I use dynamic it is not invoking