Get Number of days between two dates

date_diff.php

<?php
if (!function_exists('get_days_number')) {
    /**
     * Get Number of days between tho dates
     *
     * @param  string $first_date First date
     * @param  string $second_date Second date
     * @return float
     */
    function get_days_number($first_date, $second_date)
    {
        // Return the number of days between the two dates:
        return round(abs(strtotime($first_date) - strtotime($second_date)) / 86400);
    }
}

echo get_days_number(date('Y-m-d'), '2016-10-15');