php无限分类 构建树形结构 递归求所有下线用户

　　test:

 1,  'parentid' => 0, 'name' => 'PHP'],
	['id' => 2, 'parentid' => 1, 'name' => 'PHP_Framework'],
	['id' => 42, 'parentid' => 1, 'name' => 'DevTools'],
	['id' => 3, 'parentid' => 2, 'name' => 'ThinkPHP5'],
	['id' => 4, 'parentid' =