[PHP知识库]php用户选择几月第几个星期几获得具体日期

/**
 * @param $year_month 需要计算的年月
 * @param $how_many   第几个日期
 * @param $what_week  选择周几
 * @return array|string[]
 */
public function generation($year_month,$how_many,$what_week)
{
    \Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
    /*$year_month = "2021-07";
    $how_many = '3'; //选择第几个  1.第一个····5第五个、6最后一个
    //1周一，2周二，3周三，4周四，5周五，6周六，7周日，8自然日，9工作日，10周末
    $what_week = '9'; //选择周几
    */
    if ($what_week < 7){//周一-周六
        $what_week = $what_week;
        $week_info = $this->get_week($how_many,$what_week,$year_month);
        $data =array(
            'start_time' =>  $week_info,
            'end_time' =>$week_info
        );
        return $data;
    }elseif ($what_week == 7){//周日
        $what_week = 0;
        $week_info = $this->get_week($how_many,$what_week,$year_month);
        $data =array(
            'start_time' =>  $week_info,
            'end_time' =>$week_info
        );
        return $data;
    }elseif ($what_week == 8){//返回当月一号
        if ($how_many <= 5){
            $week_info =  $year_month.'-0'.$how_many;
        }else{
            $week_info = date('Y-m-d', strtotime(date('Y-m-01', strtotime($year_month.'-01')) . ' 1 month -1 day'));
        }
        $data =array(
            'start_time' =>  $week_info,
            'end_time' =>$week_info
        );
        return $data;
    }elseif ($what_week == 9){//工作日计算
        $start_time =  $year_month.'-01'; //當月第一天
        $end_time = date('Y-m-d', strtotime(date('Y-m-01', strtotime($year_month.'-01')) . ' 1 month -1 day'));
        $info = $this->get_work_day($start_time,$end_time);//获取当月所有的工作日
        $workday = $info['workday'];
        if ($how_many <= 5){ //输入的第几周大于实际的周数，默认使用最后一周
            $week_info = $workday[$how_many-1];
        }else{
            $work_num = count($workday);
            $week_info = $workday[$work_num-1];
        }
        $data =array(
            'start_time' =>  $week_info,
            'end_time' =>$week_info
        );
        return $data;

    }elseif ($what_week == 10){ //获取周末
        //周六
        $start_time = $this->get_week($how_many,6,$year_month);
        $start = explode('-',$start_time);
        //周日
        $end_time = $this->get_week($how_many,0,$year_month);
        $end = explode('-',$end_time);
        if ($start[2] >$end[2]){
            $day = $end[2]-1;
            $end_time = $end_time;
            $start_time = $end[0].'-'.$end[1].'-'.$day;
        }
        $data =array(
           'start_time' =>  $start_time,
            'end_time' =>$end_time
        );
        return $data;
    }

}

/**
 * @param $what_week
 * @param $week
 * @param $year_month
 * @return mixed  计算第几个周几的日期
 */
public function get_week($week,$what_week,$year_month){
    if(empty($year_month)){
        $year_month = date("Y-m");
    }
    $maxDay  = date('t', strtotime($year_month."-01"));
    //计算出当前月份所有周几
    $mondays = array();
    for($i=1; $i<=$maxDay; $i++){
        if(date('w', strtotime($year_month."-".$i)) == $what_week){
            $mondays[] = $year_month."-".($i>9?'':'0').$i;
        }
    }
    //获取当月有几个周几
    if ($week >= count($mondays)){ //输入的第几周大于实际的周数，默认使用最后一周
        $week_num =  count($mondays);
        $week_info = $mondays[$week_num-1];
    }else{
        $week_info = $mondays[$week-1];
    }
    return $week_info;
}
/**
 * @param $start_time  月份第一天
 * @param $end_time    月份最后一天
 * @return array|array[] 每个月所有的工作日和周六周日日期
 */
function get_work_day($start_time,$end_time)
{
    $start_time = empty($start_time)?time():strtotime($start_time);
    $end_time = empty($end_time)?time():strtotime($end_time)+86400;//最后一天也算
    if($end_time<=$start_time){
        return array();
    }
    $days = ($end_time - $start_time)/86400;
    $work_day_array = array();//工作日
    $Weekend_day_array = array();//周末
    for ($i=0; $i < $days ; $i++) {
        $timer = $start_time + 86400*$i;
        $num= date("N",$timer);
        if($num == 6 || $num == 7) {
            $Weekend_day_array[] = date('Y-m-d',$timer);
        }else{
            $work_day_array[] = date('Y-m-d',$timer);
        }
    }
    return array(
        'workday'=>$work_day_array,      //所有工作日
        //'weekend'=>$Weekend_day_array //所有周末
    );
}