使用字段旁边的Codeigniter显示错误

Question

How can I display each error next to input field, or only one error for all fields (like "all fields are required") down below? I prefer each error next to input.

1. View: I'm using form_open and later form_input. form_eror doesn't work.

   // INPUT FORM FOR PRODUCT INSERT
   
   // Form open
   echo form_open('insert_product',array('id' =>'form')); 
   
   //all form inputs
   
   // Name
   echo form_label('Name  ','name');
   $name = array(
       'name'        => 'productName',
       'id'          => 'productName',
       'placeholder' => 'Enter product name',
   
   );
   echo form_input($name,  set_value('name'));
   echo form_error('name');
   

2. Controller validation rules in array:

   // Define validation rules for form inputs
   $validation_rules = array(
       //Name
       array(
           'field' => 'productName',
           'label' => 'Product name',
           'rules' => 'required|min_length[3]'   
       ),
   

3. Validation check in controller :

   //Check validation
   if ( $this->form_validation->run() == true ) {
   
        //Preparing input data, keys of array are the same as fields in database table
           $data = array(
               'Name'            => $this->input->post('productName'),
               'Description'     => $this->input->post('productDescription'),
               'Production_date' => date('Y-m-d',  strtotime( $this->input->post('productProduction_date' ))),
               'Expiry_date'     => date('Y-m-d',  strtotime( $this->input->post('productExpiry_date' ))),
               'Price'           => $this->input->post('productPrice'),
               'Currency'        => $this->input->post('productCurrency'),
               'EAN_code'        => $this->input->post('productEAN_code'),
               'Weight'          => $this->input->post('productWeight'),
               'Weight_unit'     => $this->input->post('productWeight_unit')
           );
   
           //Transfer data to model and get message from model
          $row = $this->ProductModel->insert_product($data);
   
           //get answer
           if ($row) {
              echo "Product successfully added to database";
           }else {
               echo 'There was an error inserting data in database '.json_encode($row);
           }
   
   }
   else {
   
       echo validation_errors();
   }