SELECT selected CHECKBOX and update in selected row into DATABASE in Codeigniter

Code:

<input type="checkbox" name="sample[]" value="0"/>

You've hardcoded sample variable values to 0. You should update these to what-ever values you need to come back from the form.

I want fix value when i am update that value=0 is static
but i did not get row id,
when i am update this code then value="0" consider as a id so i am confused how to get particular row id