表单传递过来的数据：

array(9) {
  ["tid747"] => array(2) {
    [0] => string(3) "163"
    [1] => string(3) "162"
  }
  ["pid"] => array(2) {
    [0] => string(3) "747"
    [1] => string(3) "750"
  }
  ["mid"] => array(2) {
    [0] => string(2) "14"
    [1] => string(2) "14"
  }
  ["tid750"] => array(1) {
    [0] => string(3) "162"
  }
  ["action"] => string(4) "edit"
  ["tid"] => string(3) "525"
  ["cid"] => string(3) "723"
  ["ccid"] => string(3) "728"
  ["id"] => string(3) "883"
}

原多维数组：

array(2) {
  [0] => array(2) {
    [0] => array(2) {
      ["class_id"] => string(3) "883"
      ["province"] => string(3) "747"
    }
    [1] => array(2) {
      ["class_id"] => string(3) "883"
      ["province"] => string(3) "747"
    }
  }
  [1] => array(1) {
    [0] => array(2) {
      ["class_id"] => string(3) "883"
      ["province"] => string(3) "750"
    }
  }
}

改变成一维数组：

array(3) {
  [0] => array(3) {
    ["class_id"] => string(3) "883"
    ["province"] => string(3) "747"
    ["tid"] => string(3) "163"
  }
  [1] => array(3) {
    ["class_id"] => string(3) "883"
    ["province"] => string(3) "747"
    ["tid"] => string(3) "162"
  }
  [2] => array(3) {
    ["class_id"] => string(3) "883"
    ["province"] => string(3) "750"
    ["tid"] => string(3) "162"
  }
}

代码：

    //保存表单试卷
    if (request()->isPost()){
      dump(input(''));
      //循环省份
      if(count($pid)>0 && $id){
        for($i=0;$i<count($pid);$i++){
          //循环该省的试卷ID
          $tidarr=input('tid'.$pid[$i]);//省份ID
          if(count($tidarr)>0){
            for($n=0;$n<count($tidarr);$n++){
              $dataadd1[$i][$n]['class_id']=$id;
              $dataadd1[$i][$n]['province']=$pid[$i];
              $dataadd1[$i][$n]['tid']=$tidarr[$n];
              $dataadd[] = [
                'class_id' =>$id,
                'province' =>$pid[$i],
                'tid' =>$tidarr[$n],
              ];
              
            }
          }
        
        }
        if(count($dataadd)>0){
//          $rs = Db::name('class_test')->insert($dataadd);
//          if($rs){
//            $this->success('成功!');
//          }else{
//            $this->error('失败');
//          }
        }
      }
      
      
      dump($dataadd1);
      dump($dataadd);die;
      
    }