I am stuck with a probably very simple problem.
I have created a simple content type "reservation" with an integer field called "field_km" and of default value 50.
On the node creation form, I want to have a markup field showing the value of the "field_km" field.
So, I have created a simple myresa module, with the following code :

    < ?php
    // $Id$
    
    /**
    * @file
    * Drupal Module : myresa
    * Adds custom code specific to this Drupal 7 site.
    */
    
    function myresa_form_reservation_node_form_alter(&$form, &$form_state, $form_id) {
    $form[‘box’] = array(
    ‘#type’ => ‘markup’,
    ‘#prefix’ => ‘’,
    ‘#suffix’ => ‘’,
    ‘#markup’ => ‘Price not computed',
    ) ;
    
    $form[‘mybtn’] = array(
    ‘#type’ => ‘button’,
    ‘#id’ => ‘mybtn’,
    ‘#ajax’ => array(
    ‘callback’ => ‘myresa_callback’,
    ‘wrapper’ => ‘box’,
    ‘name’ => ‘mybtn1’,
    ),
    ‘#value’ => t(‘Compute the price’),
    ) ;
    }
    
    function myresa_callback($form, $form_state) {
    $element = $form[‘box’] ;
    $element[‘#markup’] = «The price for » . $form_element[‘field_km’][‘#default_value’] . » km is 35 euros» ;
    return $element ;
    }

The form shows the 'box' markup, the button, and when clicked the button activates the callback and shows the wanted text, but not the value of 'field_km'.
It is probably a simple syntax mistake, but it beats me.

Thank you very much in advance for sparing 30 seconds to help ;-))