帮忙转化一个数组,该怎么处理

$arr = array(
    array('goods_id'=>'1','sku_id'=>'001','zk'=>'0.5'),
    array('goods_id'=>'1','sku_id'=>'002','zk'=>'0.5'),
    array('goods_id'=>'1','sku_id'=>'006','zk'=>'0.5'),

    array('goods_id'=>'2','sku_id'=>'003','zk'=>'0.8'),
    array('goods_id'=>'2','sku_id'=>'004','zk'=>'0.8'),
);

$_arr = array(
    '1' =>array(
                'zk'=>'0.5',
                'mx'=>array(
                    array('sku_id'=>'001','zk'=>'0.5'),
                    array('sku_id'=>'002','zk'=>'0.5'),
                    array('sku_id'=>'006','zk'=>'0.5'),
                ),
    '2' =>array(
                'zk'=>'0.8',
                'mx'=>array(
                    array('sku_id'=>'003','zk'=>'0.8'),
                    array('sku_id'=>'004','zk'=>'0.8'),
                ),
    )
);

'1','sku_id'=>'001','zk'=>'0.5'),
    array('goods_id'=>'1','sku_id'=>'002','zk'=>'0.5'),
    array('goods_id'=>'1','sku_id'=>'006','zk'=>'0.5'),

    array('goods_id'=>'2','sku_id'=>'003','zk'=>'0.8'),
    array('goods_id'=>'2','sku_id'=>'004','zk'=>'0.8'),
);

foreach($arr as $v){
    $tmp[$v['zk']]['zk']=$v['zk'];
    $tmp[$v['zk']]['mx'][]=array_splice($v,1,2);
}
print_r(array_values($tmp));