项目中会经常遇到需要递归的地方，分享一个正在用的一个递归查询。虽然递归有时候会慢，但是还没有找到个好的解决办法，如果有好的办法，请分享一下。

     $value){
                      if($value['pid'] == $pid){
                              self::$treeList[] = $value;                             unset($data[$key]);                             self::create($data,$value['id']);                     }             }             return self::$treeList;     }     /**      * 分类数据处理      * @end      */        /**      * @var object 对象实例      */     protected static $instance;     /**      * 配置参数      * @var array      */     protected static $config = [         'id'    => 'id',    // id名称         'pid'   => 'pid',   // pid名称         'title' => 'title', // 标题名称         'child' => 'child', // 子元素键名         'html'  => '┝ ',   // 层级标记         'step'  => 4,       // 层级步进数量     ];     /**      * 架构函数      * @param array $config      */     public function __construct($config = [])     {
          self::$config = array_merge(self::$config, $config);     }     /**      * 配置参数      * @param  array $config      * @return object      */     public static function config($config = [])     {
          if (!empty($config)) {
              $config = array_merge(self::$config, $config);         }         if (is_null(self::$instance)) {
              self::$instance = new static($config);         }         return self::$instance;     }     /**      * 将数据集格式化成层次结构      * @param array/object $lists 要格式化的数据集，可以是数组，也可以是对象      * @param int $pid 父级id      * @param int $max_level 最多返回多少层，0为不限制      * @param int $curr_level 当前层数      * @return array      */     public static function toLayer($lists = [], $pid = 0, $max_level = 0, $curr_level = 0)     {
          $trees = [];         $lists = array_values($lists);         foreach ($lists as $key => $value) {
              if ($value[self::$config['pid']] == $pid) {
                  if ($max_level > 0 && $curr_level == $max_level) {
                      return $trees;                 }                 unset($lists[$key]);                 $child = self::toLayer($lists, $value[self::$config['id']], $max_level, $curr_level + 1);                 if (!empty($child)) {
                      $value[self::$config['child']] = $child;                 }                 $trees[] = $value;             }         }         return $trees;     }     /**      * 将数据集格式化成列表结构      * @param  array|object   $lists 要格式化的数据集，可以是数组，也可以是对象      * @param  integer $pid        父级id      * @param  integer $level      级别      * @return array 列表结构(一维数组)      */     public static function toList($lists = [], $pid = 0, $level = 0)     {
          if (is_array($lists)) {
              $trees = [];             foreach ($lists as $key => $value) {
                  if ($value[self::$config['pid']] == $pid) {
                      $title_prefix   = str_repeat(" ", $level * self::$config['step']).self::$config['html'];                     $value['level'] = $level + 1;                     $value['title_prefix']  = $level == 0 ? '' : $title_prefix;                     $value['title_display'] = $level == 0 ? $value[self::$config['title']] : $title_prefix.$value[self::$config['title']];                     $trees[] = $value;                     unset($lists[$key]);                     $trees   = array_merge($trees, self::toList($lists, $value[self::$config['id']], $level + 1));                 }             }             return $trees;         } else {
              foreach ($lists as $key => $value) {
                  if ($value[self::$config['pid']] == $pid && is_object($value)) {
                      $title_prefix   = str_repeat(" ", $level * self::$config['step']).self::$config['html'];                     $value['level'] = $level + 1;                     $value['title_prefix']  = $level == 0 ? '' : $title_prefix;                     $value['title_display'] = $level == 0 ? $value[self::$config['title']] : $title_prefix.$value[self::$config['title']];                     $lists->offsetUnset($key);                     $lists[] = $value;                     self::toList($lists, $value[self::$config['id']], $level + 1);                 }             }             return $lists;         }     }     /**      * 根据子节点返回所有父节点      * @param  array  $lists 数据集      * @param  string $id    子节点id      * @return array      */     public static function getParents($lists = [], $id = '')     {
          $trees = [];         foreach ($lists as $value) {
              if ($value[self::$config['id']] == $id) {
                  $trees[] = $value;                 $trees   = array_merge(self::getParents($lists, $value[self::$config['pid']]), $trees);             }         }         return $trees;     }     /**      * 获取所有子节点id      * @param  array  $lists 数据集      * @param  string $pid   父级id      * @return array      */     public static function getChildsId($lists = [], $pid = '')     {
          $result = [];         foreach ($lists as $value) {
              if ($value[self::$config['pid']] == $pid) {
                  $result[] = $value[self::$config['id']];                 $result = array_merge($result, self::getChildsId($lists, $value[self::$config['id']]));             }         }         return $result;     }     /**      * 获取所有子节点      * @param  array  $lists 数据集      * @param  string $pid   父级id      * @return array      */     public static function getChilds($lists = [], $pid = '')     {
          $result = [];         foreach ($lists as $value) {
              if ($value[self::$config['pid']] == $pid) {
                  $result[] = $value;                 $result = array_merge($result, self::getChilds($lists, $value[self::$config['id']]));             }         }         return $result;     }     /**      * 根据子分类获取顶级分类      * @param  string $id   子分类id      * @return  int      */     public static function getNavPid($id){
          $catId = Category::get($id);         if($catId['pid'] != 0){
              return self::getNavPid($catId['pid']);         }         return $catId['id'];     } }