Caculate digital root – Add a simple & easy function for PHP/HTM site by claytoncheung

Background: My site is running on PHP and using HTM as template. Requirements: 1) make a new page like “http://www.thonky.com/digital-root-calculator/” , let my user to input their birthday : DAY/ MONTH/ YEAR and calculate the Digital Root of it… (Budget: $240-$360 HKD, Jobs: HTML, PHP)