在Jquery模板（.tpl文件）中获取数组键

I have created an array named 'DefaultOptions' in PHP which resulted like this

Key   Value

1   "Option1"
2   "Option2"
3   "Option3"
4   "Option4"
6   "Option6"

And in ".tpl" file i tried to create a Dropdown with the above result like this

<select name="DefaultOptions" id="DefaultOptions">
                    {#foreach $T.DefaultOptions as reportoption extData=$T}
                        <option value="{$T.key}">{$T.reportoption}</option>
                    {#/for}
                    </select>

This resulted in following output

<select id="DefaultOptions" name="DefaultOptions">
 <option value="">Option1</option>
 <option value="">Option2</option>
 <option value="">Option3</option>
 <option value="">Option4</option>
 <option value="">Option6</option>
</select>

Here Option Names are printed fine but Value is EMPTY. In value (attribute) the KEY need to set.

No error is coming but seems some wrong syntax to get the Key.

What is the right syntax to get array KEY here.