AngularJS implementation of chained select boxes with ajax calls for data
let's make it as a custom directive

fully functional demo
http://ng-chained-selects.appspot.com/index.html

base angular application
https://github.com/Swiip/generator-gulp-angular
(plain app is currently used)

php back-end to support ajax requests

http://ng-chained-selects.appspot.com/

https://cloud.google.com/appengine/docs/php/gettingstarted/uploading

option tree sample

####Note 2 ajax calls are involved:

• initial tree returns an object with options array on each level (1, 2, 3, etc.)
• options list returns an array of options which are the children(leaves) of the parent option

initId - initial value of the select box chain, it also determines how many select boxes in the chain. Also picked value is bound to the variable provided as initId.

TODO: bower package (javascript)
TODO: add interfaces for the tree and options services(php)