Flatten a multidimensional array and remove duplicate values

Question

all I want to remove the duplicate value from this Array

Array
(
    [0] => Array
        (
            [0] => Ajay Patel
            [1] => Tag 1
        )

    [1] => Array
        (
            [0] => Tag 1
            [1] => Tag 3
        )

    [2] => Array
        (
        )

    [3] => Array
        (
        )

    [4] => Array
        (
        )

)

I tried this solution from How to remove duplicate values from a multi-dimensional array in PHP

$result2 = array_map("unserialize", array_unique(array_map("serialize", $result2)));

But i think something is wrong here, i am getting this as result.

Array
(
    [0] => Array
        (
            [0] => Ajay Patel
            [1] => Tag 1
        )

    [1] => Array
        (
            [0] => Tag 1
            [1] => Tag 3
        )

    [2] => Array
        (
        )

)

What i want is

Array
            (
                [0] => Ajay Patel
                [1] => Tag 1
                [2] => Tag 3
            )

Tag 1 is removed because its 2 times...

Answer 1

$result2 = array_unique(call_user_func_array('array_merge',$result2));

In modern PHP, the same technique can be written as:

$result2 = array_unique(array_merge(...$result2));