How to add confirmation pop up box for delete button in php

I am new to php . how do i add a confirmation pop up box to this. Are you sure you want to remove and if it is yes to remove the file and if it is no then to remain in the same page

<button id='removebtn' name='removebtn' class='button'  onclick=" removeFile(<?php print $this->prv_data['attachment_id'] ?>);">Remove File</button>