php unique values from multi-dimensional array

Question

I am strugglin' with following array to retreive the unique values. This array comes from a nested product assembly structure. Tried several techniques but no result yet. Maybe someone can help me with this? Thanks in advance!

Array
(
    [0] => Array
        (
            [product_ID] => 1
            [amount] => 2.00
        )


[1] => Array
    (
        [product_ID] => 1
        [amount] => 2.00
    )

[2] => Array
    (
        [product_ID] => 1
        [amount] => 2.00
    )

[3] => Array
    (
        [product_ID] => 5
        [amount] => 6.00
    )


) 

Goal is to retreive an array like:

 Array ( [0] => Array ( [product_ID] => 1 [amount] => 2.00 ) 
 
\n\n
 [1] => Array ( [product_ID] => 5 [amount] => 6.00 ) 
\n\n
 )  

Answer 1

因为索引是唯一的，所以最简单的方法也可能是提取通过product_ID建立索引的数组：

$result = array_column($array, null, 'product_ID');