<form enctype='application/json'>
          <input name='wow[such][deep][3][much][power][!]' value='Amaze'>
        </form>

        // produces
        {
            "wow":  {
                "such": {
                    "deep": [
                        null
                    ,   null
                    ,   null
                    ,   {
                            "much": {
                                "power": {
                                    "!":  "Amaze"
                                }
                            }
                        }
                    ]
                }
            }
        }