class Totree{
    public function school_totree(){
        $list=[
            ['id'=>1,'name'=>'学校','pid'=>0],
            ['id'=>2,'name'=>'一年级','pid'=>1],
            ['id'=>3,'name'=>'1班','pid'=>5],
            ['id'=>4,'name'=>'2班','pid'=>2],
            ['id'=>5,'name'=>'二年级','pid'=>1],
            ['id'=>6,'name'=>'3班','pid'=>5],
            ['id'=>7,'name'=>'4班','pid'=>5],
            ['id'=>8,'name'=>'4班','pid'=>2],
        ];
        $res=$this->totree($list,$pid=0,$level=0);
        echo '<pre>';
        var_dump($res);
    }
    /**
     * @description: 转成树形数据
     * @param {*} $list 初始数据
     * @param {*} $pid 父id
     * @param {*} $level 层级
     * @param {*} $pid_name pid字段名称 默认pid
     * @param {*} $id_name  主键id 名称
     * @return {*}
     */    
    public function totree($list,$pid=0,$level=0,$pid_name='pid',$id_name='id')
    {
        $arr=[];
        $level++;
        foreach($list as $k => $v){
            if($pid==$v[$pid_name]){
                $v['level']=$level;
                $v['next']=$this->totree($list,$v[$id_name],$level,$pid_name,$id_name);
                $arr[]=$v;
            }
        }
        return $arr;
    }
}
    /**
     * @description: 转成树形显示-
     * @param {*} $result 结果
     * @param {*} $list 初始数据
     * @param {*} $pid 父id
     * @param {*} $level 层级
     * @param {*} $pid_name pid字段名称 默认pid
     * @param {*} $id_name  主键id 名称
     * @return {*}
     */    
    public function totreestr($list,$pid=0,$level=0,$pid_name='pid',$id_name='id')
    {
        $arr=[];
        $level++;
        foreach($list as $k => $v){
            if($pid==$v[$pid_name]){
                // $v['level']=$level;
                $name_str='';
                if($level>1){
                    for($i=0;$i<$level-1;$i++){
                        $name_str=$name_str.'▬';
                    }
                }
                $v['name']=$name_str.$v['name'];
                $arr[]=$v;
                $next=$this->totreestr($list,$v[$id_name],$level,$pid_name,$id_name);
                if(!empty($next)){
                    foreach($next as $kk => $vv){
                        $arr[]=$vv;
                    }
                }
            }
        }
        return $arr;
    }