PHP获取指定年月日的开始和结束时间戳

/**
 * 获取指定年月的开始和结束时间戳
 * @param string $day    年月日
 * @param int $type    类型0整月1整天2整年3全部4季度
 * @return array(开始时间,结束时间)
 */
function fristAndLast($day='',$type=0){
    $day=$day ? $day : date('Y-m-d');
    $dayarr=explode('-',$day);
    $y = $dayarr[0] ? $dayarr[0] : date('Y');
    $m = $dayarr[1] ? $dayarr[1] : date('m');
    if(!empty($type)){
        if($type==1){
            $firstday = date("Y-m-01",strtotime($day));
            $lastday = date("d",strtotime("$firstday +1 month -1 day"));
            $d = $dayarr[2] ? $dayarr[2] : $lastday;
            return ["firsttime"=>strtotime($day),"lasttime"=>mktime(23,59,59,$m,$d,$y)];
        }else if($type==2){
            return ["firsttime"=>strtotime($y.'-01-01'),"lasttime"=>mktime(23,59,59,12,31,$y)];
        }else if($type==3){
            return ["firsttime"=>strtotime('1970-01-01'),"lasttime"=>mktime(23,59,59,12,31,$y)];
        }else if($type==4){
            $season = ceil(date('n')/3);
            $quarter_start=date('Y-m-01',mktime(0,0,0,($season - 1) *3 +1,1,date('Y')));// 季度开始
            $quarter_end=date('Y-m-t',mktime(0,0,0,$season * 3,1,date('Y')));// 季度结束
            return ["firsttime"=>strtotime($quarter_start),"lasttime"=>strtotime($quarter_end.' 23:59:59')];
        }
    }else{
        $d =date('t', strtotime($y.'-'.$m));
        return ["firsttime"=>strtotime($y.'-'.$m),"lasttime"=>mktime(23,59,59,$m,$d,$y)];
    }
}