array functions, how to merge the same array items?

[blackhorse]

I have two arrays

$products_id={100, 101, 102, 101};
$quantity={10, 10, 10, 10}

for products_id 100, 101, 102, 101, I have 10 items each in the shopping cart.

How I walk though this array, and merge the emelments with the same products_id and add up the quantity. The new arrays I want are

$products_id={100, 101, 102};
$quantity={10, 20, 10};

Thanks!

[m_tt]

Have you tried array_unique?

[blackhorse]

I have two arrays work together
$products_id={100, 101, 102, 101};
$quantity={10, 10, 10, 10}

array_unique will make the $products_id=={100, 101, 102};
But I also need the $quantity={10, 20, 10}

I will read through the array functions to see if I can come up with a solution, any one has some more tips to help me out? thanks!