下面这堆数组gid相同的，要求Num累加，gid不同的不操作直接显示，数组去重如何实现？

Array
(
    [0] => Array
        (
            [id] => 1
            [no] => WF20170001
            [wid] => 1
            [gid] => 1
            [num] => 4
            [price] => 2.55
            [amount] => 10.20
            [buyer] => 顾文君
            [invoice] => 123456789
            [date] => 2017-03-28
            [remarks] => 测试数据
            [cid] => pc001
            [class] => 办公用品
            [name] => 笔记本电脑
            [type] => Acer Aspire E1-410G
            [unit] => 台
            [warehouse_name] => 办公用品仓库
        )

    [1] => Array
        (
            [id] => 3
            [no] => WF20170001
            [wid] => 1
            [gid] => 5
            [num] => 5
            [price] => 100.00
            [amount] => 500.00
            [buyer] => 顾文君
            [invoice] => 1231241
            [date] => 2017-04-14
            [remarks] => 入库测试
            [cid] => tf001
            [class] => 办公用品
            [name] => 打印机碳粉
            [type] => 88A
            [unit] => 支
            [warehouse_name] => 办公用品仓库
        )

    [2] => Array
        (
            [id] => 4
            [no] => WF20170001
            [wid] => 1
            [gid] => 2
            [num] => 1
            [price] => 4500.00
            [amount] => 4500.00
            [buyer] => 张秀珍
            [invoice] => 4558895
            [date] => 2017-04-09
            [remarks] => 入库测试
            [cid] => pc002
            [class] => 办公用品
            [name] => 笔记本电脑
            [type] => Acer Aspire E5-571G-58WT
            [unit] => 台
            [warehouse_name] => 办公用品仓库
        )

    [3] => Array
        (
            [id] => 5
            [no] => WF20170002
            [wid] => 1
            [gid] => 3
            [num] => 1
            [price] => 88.00
            [amount] => 88.00
            [buyer] => 顾文君
            [invoice] => 556789
            [date] => 2017-04-09
            [remarks] => 测试数据
            [cid] => ow
            [class] => 办公用品
            [name] => 万用表
            [type] => 万用表
            [unit] => 台
            [warehouse_name] => 办公用品仓库
        )

    [4] => Array
        (
            [id] => 12
            [no] => WF20170001
            [wid] => 1
            [gid] => 1
            [num] => 1
            [price] => 2.55
            [amount] => 2.55
            [buyer] => 顾文君
            [invoice] => 53412312
            [date] => 2017-06-05
            [remarks] => 无
            [cid] => pc001
            [class] => 办公用品
            [name] => 笔记本电脑
            [type] => Acer Aspire E1-410G
            [unit] => 台
            [warehouse_name] => 办公用品仓库
        )

)