Pattern for getting ands setting variables across environments with Drupal and PHP. Trying to reconcile with a twelve factor approach, and Drupal's insistence on storing things in a database at any given opportunity.

for_deployment.sh

## vars specific to the environment:
drush vset('facebook_app_id', get_env('facebook_app_id'))

## fetching changes from code
drush fu all

## fetching changes from code
drush cc all

in_code.js

// lets say I want to call facebook asynchronously now, 
// I'd pull like so:
$.getScript('//connect.facebook.net/en_UK/all.js', function() {
  window.fbAsyncInit = function() {
    FB.init({
      appId: Drupal.myModule.facebook_app_id,
    });
  };
});

in_code.php

<?php 

$handy_value = variable_get('my_form_element')

// set our value first that the facebook code uses
drupal_add_js(array('myModule' => array('facebook_app_id' => $handy_value)), 'setting');

// then include the facebook code, makign
drupal_add_js(drupal_get_path('module', 'myModule') . '/facebook.js', );