PHP | Future Dates | Exam 22 Dec 2014

<?php
    // patterns
    $numsPattern = '/[^a-zA-Z0-9]+?([0-9]+)[^a-zA-Z0-9]+?/';
    $datePattern = '/([0-9]{4})-([0-9]{2})-([0-9]{2})/';

    // extracting information
    preg_match_all($numsPattern, $_GET['numbersString'], $nums);
    preg_match_all($datePattern, $_GET['dateString'], $dates, PREG_SET_ORDER);

    // getting sum backwards
    $backwardsNum = numBackwards(array_sum($nums[1]));

    // Printing results
    if(!empty($dates)) {
        echo '<ul>';
        foreach($dates as $d) {
            $newDate = new DateTime($d[0]);
            // var_dump($newDate); // date befor modification
            addDays($newDate, $backwardsNum);
            // var_dump($newDate); // modified date with $backwardsNum
            echo '<li>' . $newDate->format('Y-m-d') . '</li>';
        }
        echo '</ul>';
    } else {
        echo '<p>No dates</p>';
    }

    function numBackwards($num) {
        $numStr = (string) $num;
        preg_match_all("/[0-9]/", $numStr, $numArr);
        return (int) implode(array_reverse($numArr[0]));
    }

    function addDays(DateTime $date, $days) {
        $date->add(new DateInterval('P' . $days . 'D'));
    }
?>