如何在php中替换内部数组

我有一个数组，如下所示：

    Array
    (
        [154541] => Array
            (
                **[3831211] => Array
                    (
                        [34443] => 34443
                        [34444] => 34444
                        [34438] => 34438
                        [34442] => 34442
                        [34450] => 34450
                    )**
            )
        [154514] => Array
            (
                **[3830597] => Array
                    (
                        [34442] => 34442
                        [34450] => 34450
                        [34443] => 34443
                        [34444] => 34444
                        [34438] => 34438
                    )**
            )
        [154477] => Array
            (
                **[3829564] => Array
                    (
                        [34442] => 34442
                        [34444] => 34444
                        [34438] => 34438
                        [34450] => 34450
                        [34443] => 34443
                    )**
                [3830046] => Array
                    (
                        [34442] => 34442
                        [34444] => 34444
                        [34443] => 34443
                        [34438] => 34438
                        [34450] => 34450
                    )
            )
        [154474] => Array
            (
                [3829402] => Array
                    (
                        [34442] => 34442
                        [34450] => 34450
                        [34443] => 34443
                        [34438] => 34438
                        [34444] => 34444
                    )
            )
        [154472] => Array
            (
                [3831553] => Array
                    (
                        [34443] => 34443
                        [34450] => 34450
                        [34438] => 34438
                        [34444] => 34444
                        [34442] => 34442
                    )
                [3829803] => Array
                    (
                        [34443] => 34443
                        [34444] => 34444
                        [34450] => 34450
                        [34442] => 34442
                        [34438] => 34438
                    )
                [3829802] => Array
                    (
                        [34443] => 34443
                        [34444] => 34444
                        [34438] => 34438
                        [34450] => 34450
                        [34442] => 34442
                    )
                [3831552] => Array
                    (
                        [34444] => 34444
                        [34450] => 34450
                        [34443] => 34443
                        [34442] => 34442
                        [34438] => 34438
                    )
                [3830078] => Array
                    (
                        [34444] => 34444
                        [34442] => 34442
                        [34443] => 34443
                        [34438] => 34438
                        [34450] => 34450
                    )
            )
)

现在，我想用我新生成的名为$alerts的数组来替换内部数组（我在上面的数组中将该内部数组制作为**）。

我不知道如何用$alerts数组替换内部数组。