Non-recursive method to implement PHP tree

The following brings you a method to implement PHP trees without recursion. The content is quite good, so I will share it with you now and give it as a reference.

PHP tree-implementation method that does not require recursion

/**
 * 创建父节点树形数组
 * 参数
 * $ar 数组，邻接列表方式组织的数据
 * $id 数组中作为主键的下标或关联键名
 * $pid 数组中作为父键的下标或关联键名
 * 返回 多维数组
 **/
function find_parent($ar, $id='id', $pid='pid') {
 foreach($ar as $v) $t[$v[$id]] = $v;
 foreach ($t as $k => $item){
  if( $item[$pid] ){
   if( ! isset($t[$item[$pid]]['parent'][$item[$pid]]) )
     $t[$item[$id]]['parent'][$item[$pid]] =& $t[$item[$pid]];
  }
 }
 return $t;
}


/**
 * 创建子节点树形数组
 * 参数
 * $ar 数组，邻接列表方式组织的数据
 * $id 数组中作为主键的下标或关联键名
 * $pid 数组中作为父键的下标或关联键名
 * 返回 多维数组
 **/
function find_child($ar, $id='id', $pid='pid') {
 foreach($ar as $v) $t[$v[$id]] = $v;
 foreach ($t as $k => $item){
  if( $item[$pid] ) {
   $t[$item[$pid]]['child'][$item[$id]] =& $t[$k];
  }
 }
 return $t;
}

  $data = array(
   array('ID'=>1, 'PARENT'=>0, 'NAME'=>'祖父'),
   array('ID'=>2, 'PARENT'=>1, 'NAME'=>'父亲'),
   array('ID'=>3, 'PARENT'=>1, 'NAME'=>'叔伯'),
   array('ID'=>4, 'PARENT'=>2, 'NAME'=>'自己'),
   array('ID'=>5, 'PARENT'=>4, 'NAME'=>'儿子'),
  );

  $p = find_parent($data, 'ID', 'PARENT');
  $c = find_child($data, 'ID', 'PARENT');
  Print_r ($c);

##Execution Effect:

Array
(
  [1] => Array
    (
      [ID] => 1
      [PARENT] => 0
      [NAME] => 祖父
      [child] => Array
        (
          [2] => Array
            (
              [ID] => 2
              [PARENT] => 1
              [NAME] => 父亲
              [child] => Array
                (
                  [4] => Array
                    (
                      [ID] => 4
                      [PARENT] => 2
                      [NAME] => 自己
                      [child] => Array
                        (
                          [5] => Array
                            (
                              [ID] => 5
                              [PARENT] => 4
                              [NAME] => 儿子
                            )

                        )

                    )

                )

            )

          [3] => Array
            (
              [ID] => 3
              [PARENT] => 1
              [NAME] => 叔伯
            )

        )

    )

  [2] => Array
    (
      [ID] => 2
      [PARENT] => 1
      [NAME] => 父亲
      [child] => Array
        (
          [4] => Array
            (
              [ID] => 4
              [PARENT] => 2
              [NAME] => 自己
              [child] => Array
                (
                  [5] => Array
                    (
                      [ID] => 5
                      [PARENT] => 4
                      [NAME] => 儿子
                    )

                )

            )

        )

    )

  [3] => Array
    (
      [ID] => 3
      [PARENT] => 1
      [NAME] => 叔伯
    )

  [4] => Array
    (
      [ID] => 4
      [PARENT] => 2
      [NAME] => 自己
      [child] => Array
        (
          [5] => Array
            (
              [ID] => 5
              [PARENT] => 4
              [NAME] => 儿子
            )

        )

    )

  [5] => Array
    (
      [ID] => 5
      [PARENT] => 4
      [NAME] => 儿子
    )

)

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