- date_diff: documentation ( source)
- var_dump: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$current = date('Y-m-d');
$nextBusinessDay = date('Y-m-d', strtotime($current . '+ 3 Weekday'));
$interval = date_diff($current, $nextBusinessDay);
$diff = $interval->format('%R%a days');
var_dump($interval, $diff);