render the innerHTML in symfony2
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I am designing a dynamic form builder using symfony2. when I am using the index action then I am rendering the page which is quite simmilar to the link:

    bootstrap-forms.heroku.com
In this form when I click on any link then an element is added to the div in the 'Form name' division. 
In indexAction I am rendering the complete form.I have put a `save ` button after the form name block. when I click on the save button. then a new `sub ` action is called. In this `sub` Action I want to call only this part of code in the `Form Name` block. or we can say the HTML which is in the `generated source` link.
Please help