PHP计算指定时间段内周末天数(星期日天数)、双休天数、总工作日天数

/**
 * | Author: Saron.Mo
 * | @param char|int $start_date 一个有效的日期格式，例如：20091016，2009-10-16
 * | @param char|int $end_date 同上
 * | @param int $weekend_days 一周休息天数
 * | @return array
 * | array[total_days]  给定日期之间的总天数
 * | array[total_relax] 给定日期之间的周末天数
*/
function get_weekend_days($start_date, $end_date, $weekend_days=1) {

    $data = array();
    if (strtotime($start_date) > strtotime($end_date)) list($start_date, $end_date) = array($end_date, $start_date);

    $start_reduce = $end_add = 0;
    $start_N      = date('N',strtotime($start_date));
    $start_reduce = ($start_N == 7) ? 1 : 0;

    $end_N = date('N',strtotime($end_date));

    // 进行单、双休判断，默认按单休计算
    $weekend_days = intval($weekend_days);
    switch ($weekend_days)
    {
        case 2:
            in_array($end_N,array(6,7)) && $end_add = ($end_N == 7) ? 2 : 1;
            break;
        case 1:
        default:
            $end_add = ($end_N == 7) ? 1 : 0;
            break;
    }

    $days = round(abs(strtotime($end_date) - strtotime($start_date))/86400) + 1;
    $data['total_days'] = $days;
    $data['total_relax'] = floor(($days + $start_N - 1 - $end_N) / 7) * $weekend_days - $start_reduce + $end_add;

    return $data;
}