php获取指定时间戳加减N天

/**
 * @return 获取指定时间戳加减N天 按照一天零点开始
 * @param type $time       时间戳（默认当前时间）
 * @param type $types      加一天还是减一天 （1 加 2减 默认0为当天零点）
 * @param type $tian      加或减的天数 默认1
 * @return string             返回时间戳的最终显示
 */

if (!function_exists('time_adsu')) {
    function time_adsu($timesd = '', $types = 0, $tians = 1)
    {
        if (!empty($timesd)) {
            $zhangs = date("Y-m-d", $timesd);
        } else {
            $zhangs = date("Y-m-d", time());
        }
        $xiao = strtotime($zhangs);
        $ri = date("d", $xiao);
        $yue = date("m", $xiao);
        $nian = date("Y", $xiao);
        if ($types == 1) {
            $tianshu = $ri + $tians;
            $thiems = mktime(0, 0, 0, $yue, $tianshu, $nian);
        } else if ($types == 2) {
            $tianshu = $ri - $tians;
            $thiems = mktime(0, 0, 0, $yue, $tianshu, $nian);
        } else {
            $thiems = mktime(0, 0, 0, $yue, $ri, $nian);
        }
        return $thiems;
    }
}