递归实现无限分类

$data = [
  0=>['id'=>1,'name'=>'电脑','father'=>0],
  1=>['id'=>2,'name'=>'手机','father'=>0],
  2=>['id'=>3,'name'=>'书籍','father'=>0],
  3=>['id'=>4,'name'=>'台式机','father'=>1],
  4=>['id'=>5,'name'=>'笔记本','father'=>1],
  5=>['id'=>6,'name'=>'平板','father'=>1],
  6=>['id'=>7,'name'=>'华为','father'=>2],
  7=>['id'=>8,'name'=>'苹果','father'=>2],
  8=>['id'=>9,'name'=>'教科书','father'=>3],
  9=>['id'=>10,'name'=>'小学','father'=>9],
  10=>['id'=>11,'name'=>'显示器','father'=>4],
  11=>['id'=>12,'name'=>'荣耀','father'=>7],
];
/**
 * 递归生成分类树
 * @param $data 分类数据
 * @param $pid  父级id
 * @param $level 当前层级
 * @return array
 */
function getTree($arr,$pid,$level){
  static $tree=[];
  foreach($arr as $key=>$val) {
    if($val['father'] == $pid) {
      $flag = str_repeat('└―',$level);
      $val['name'] = $flag.$val['name'];
      $tree[] = $val;
      getTree($arr , $val['id'] ,$level+1);
    }
  }
  return $tree;
}
$tree = getTree($data,0,0);
//foreach遍历输出分类数据
foreach ($tree as $val){
  echo $val['name'].'<br>';
}