This is my jquery
 $(document).ready(function(){
      $(document).on('change','#select_promo',function(){
        var price =  $('#show_promo_price').val($("#select_promo option:selected").attr('price'))
        var action = $('#show_promo_action').val($("#select_promo option:selected").attr('action'))
        var action_value = action.val();
        var price_value = price.val();


          $(document).on('click', '#promoBtn', function(e){
            var model =  $('#show_promo_model').val($("#select_model option:selected").attr('value'))
            var model_value = model.val();
           console.log(action_value);
           console.log(price_value);

        });
      });
    });

This is my HTML

                  <div class="form-group">
                    <label for="select_brand" class="col-sm-3 control-label">Brand Name</label>
                      <div class="col-sm-9">
                        <input type="hidden" class="form-control noBorder" id="show_promo_brand" name="show_promo_brand" readonly disabled>
                        <select id="select_brand" name="select_brand" class="form-control" required>

                          <option selected="" disabled="">Choose brand....</option>
                          <?php

                          $conn = $pdo->open();

                          $getBrand = $conn->prepare("SELECT * FROM brand
                                                      LEFT JOIN product_model ON brand.brand_id = product_model.brand_id
                                                      LEFT JOIN backup_sales ON backup_sales.model_id = product_model.model_id
                                                      WHERE backup_sales.po_ID = '".$_GET['po_ID']."'
                                                      GROUP BY brand.brand_name");

                          $getBrand->execute();

                          $getRowsBrand = $getBrand->fetchAll();

                          foreach($getRowsBrand as $brand)
                          {
                           echo "
                                  <option id='".$brand['brand_id']."' value='".$brand['brand_id']."'>".$brand['brand_name']."</option>
                                ";
                          }

                          $pdo->close();

                          ?>
                        </select>
                      </div>
                  </div>
                  <div class="form-group">
                    <label for="select_model" class="col-sm-3 control-label">Model Name</label>
                      <div class="col-sm-9">
                      <input type="hidden" class="form-control noBorder" id="show_promo_model" name="show_promo_model" readonly disabled>
                        <select id="select_model" name="select_model" class="form-control" required>
                        </select>
                      </div>
                  </div>