Use of ahah helper module to build dynamic forms
For building the dynamic forms in drupal, the ultimate solution is to use an ahah. Using of ahah within a form is not too difficult but it is lengthy process. Ahah hepler is shortcut solution for this, using ahah helper is too easy with no need to write a single line of javascript code.
This is an simple example of using ahah helper module within our own drupal form.
In this example I have implemented dependent select box ie options of select2 depend upon selected option of select1, this may be useful in many cases like selecting states depending upon selected country.