$items1 = array(array('id' => 1, 'pid' => 0, 'name' => '一级11','level'=>1 ),array('id' => 11, 'pid' => 0, 'name' => '一级12','level'=>1  ),array('id' => 2, 'pid' => 1, 'name' => '二级21','level'=>2 ),array('id' => 10, 'pid' => 11, 'name' => '二级22','level'=>2 ),array('id' => 3, 'pid' => 1, 'name' => '二级23','level'=>2 ),array('id' => 12, 'pid' => 11, 'name' => '二级24','level'=>2 ),array('id' => 9, 'pid' => 1, 'name' => '二级25','level'=>2 ),array('id' => 14, 'pid' => 1, 'name' => '二级26','level'=>2 ),array('id' => 4, 'pid' => 9, 'name' => '三级31','level'=>3 ),array('id' => 6, 'pid' => 9, 'name' => '三级32','level'=>3 ),array('id' => 7, 'pid' => 4, 'name' => '四级41','level'=>4 ),array('id' => 8, 'pid' => 4, 'name' => '四级42','level'=>4 ),array('id' => 5, 'pid' => 4, 'name' => '四级43','level'=>4 ),array('id' => 13, 'pid' => 4, 'name' => '四级44','level'=>4 ),array('id' => 15, 'pid' => 8, 'name' => '五级51','level'=>5 ),array('id' => 16, 'pid' => 8, 'name' => '五级52','level'=>5 ),array('id' => 17, 'pid' => 8, 'name' => '五级53','level'=>5 ),array('id' => 18, 'pid' => 16, 'name' => '六级64','level'=>6 ),
); foreach ($items1 as $item) {$temp[$item['id']]=$item;}foreach($items1 as $item){if(isset($temp[$item['pid']])){$temp[$item['pid']]['son'][]=&$temp[$item['id']];     }else{$tree[]=&$temp[$item['id']];}}function echotree($tree){foreach($tree as $data){for($i=1;$i<$data['level'];$i++){echo "-";}echo $data['name'];echo "<br/>";if($data['son']){$level+=1;echotree($data['son']);}} }echotree($tree);