PHP多维数组转换成二维数组

目前有个层次结构不规则的多维数组，需要转换成二维数组，还请请教各位大虾。
源数据如下。

$a = Array(
'0' => Array( 
    'id' => '125','level' => '0','child' => Array(
        '0' => Array('id' => '189' ,'level' => '1','child' => Array(
            '0' => Array( 'id' => '425', 'level' => '2','child' => Array(
                '0' => Array( 'id' => '385', 'level' => '3' ), 
                '1' => Array( 'id' => '782', 'level' => '3' ), ), ), ), ), 
'1' => Array('id' => '688','level' => '1'),),),);

上述格式的数组结构层次较多，看起来比较乱，如果通过chrome配合phpview插件查看的话，结构是这样的。

Array(
'0' => Array('id' => '125','level' => '0','parent_id'='0'),
'1' => Array('id' => '189','level' => '1','parent_id'='125'),
'2' => Array('id' => '425','level' => '2','parent_id'='189'),
'3' => Array('id' => '385','level' => '3','parent_id'='425'), 
'4' => Array('id' => '782','level' => '3','parent_id'='425'), 
'5' => Array('id' => '688','level' => '1','parent_id'='125'));

这里的每个parent_id是上层数组的id,第一层的parent_id是0

---

---

做个递归处理吧

function reformat($arrTmp, $parent_id=0, &$ret=null) {
    foreach($arrTmp as $k => $v) {
        $ret[$v['id']] = array('id'=>$v['id'], 'level'=>$v['level'], 'parent_id'=>$parent_id);
        if($v['child']) {
            reformat($v['child'], $v['id'], $ret);
        }
    }
    return $ret;
}

var_dump(reformat($a));

不客气

---

class Test{
    public function reduce_arr ($arr) {
        static $temp = array(); // 声明了一个静态局部变量
        foreach ($arr as $key => $val) {
            if (is_array($val)) {
                $this->reduce_arr($val);
            } else {
                $temp[$key] = $val;
            }
        }
        return $temp;
    }
}