Drupal7: JSON, hook_form_alter & hook_menu

Drupal7

This CodeLet demonstrates the use of hook_form_alter & hook_menu.
Using hook_form_alter, a text field is added to site information page. Once a API key is saved, the button has value 'Update configuration'
Using JSON menu, one can pull a node of type page, as JSON string.

CodeLet

<?php
/**
 * @file
 * 
 * @author DrupalD
 */


/**
 * Implementation of hook_menu
 * 
 * @author DrupalD
 */
function siteinfo_tweaks_menu() {
    $item = array();
    $item['JSON/%/%node'] = array(
        'type' => MENU_CALLBACK,
        'page callback' => 'siteinfo_api_data',
        'page arguments' => array(1, 2),
        'access callback' => TRUE,
    );
    
    return $item;
}


/**
 * Impementation of hook_form_alter
 * @param Array $form
 * @param Array $form_state
 * @param String $form_id
 * @author DrupalD 
 */
function siteinfo_tweaks_form_alter(&$form, &$form_state, $form_id) {
     switch ($form_id) {
        case 'system_site_information_settings':
            
            $siteAPI_key = variable_get('siteapikey', '');
            //If site API key is set, change the value of the submit button
            if ($siteAPI_key != '' ) {
                $form['actions']['submit']['#value'] = t('Update configuration');
            }
            
            //Add site API field
            $form['siteinfo_api'] = array(
              '#type' => 'fieldset',
              '#title' => t('API'),
            );
            
            $form['siteinfo_api']['siteapikey'] = array(
              '#type' => 'textfield',
              '#title' => t('Site API Key'),
              '#description' => t('Provide the API key'),
              '#attributes' => array('placeholder' =>  t('No API Key saved yet')),
              '#default_value' => variable_get('siteapikey', ''),
            );
            
            //Add a submit routine to display custom message
            $form['#submit'][1] = 'siteinfo_tweaks_submit';
            break;
    }
}

/**
 * siteinfo_tweaks_submit
 * 
 * Custom submit routine
 * 
 * @param unknown $form
 * @param unknown $form_values
 * @author DrupalD
 */
function siteinfo_tweaks_submit($form, $form_values) {
    $siteAPI_key = $form_values['values'] ['siteapikey'];
    drupal_set_message(t('Site API Key has been saved:  @api', array('@api' => $siteAPI_key)));
}


/**
 * siteinfo_api_data
 * 
 * Return API key in JSON format
 * 
 * @param unknown $siteAPI_key
 * @param unknown $nid
 * @author DrupalD
 */
function siteinfo_api_data($siteAPI_key, $node) {
    //Make sure the API key is present & its the one which has been saved previously
    if (variable_get('siteapikey') != '' && variable_get('siteapikey') == $siteAPI_key && $node->type == 'page') {
        return  drupal_json_output(array('node' => $node));
    }
    else {
        drupal_access_denied();
    }
}
?>

Info file details

name = Site infomation Tweaks
description = This module tweaks the Site infomration page. Provides a field for API key & make it available using JSON.
core = 7.x

Modules used

Custom Module

Drupal7

Drupal hook