Rank values in a multidimensional array

Question

I have an array that is already sorted but i want to give a ranking to each row. If there are matching values then it will skip a rank like 1,2,2,4,5,5,5,8.

It could potentailly be sorted on any columns but in the example below it is sorted on a and b. The rank below would be 1,1,3 as arrays 0 and 1 match.

Example array

Array
(
    [0] => Array
    (
        [rank] => 
        [a] => 5
        [b] => 4
        [c] => 1
    )

[1] => Array
    (
        [rank] => 
        [a] => 5
        [b] => 4
        [c] => 9
    )

[2] => Array
    (
        [rank] => 
        [a] => 3
        [b] => 25
        [c] => 9
    )
) 

Answer 1

Where $arr is your array:

$prev = null;

$length = count($arr);
for($i = 0; $i < $length; $i++)
{
    $sub_arr = array_slice($arr[$i], 1, 2); // keeps array('a' => , 'b' => )
    if($prev == null || $sub_arr == $prev)
    {
        $arr[$i]['rank'] = $i == 0 ? 1 : $arr[$i - 1]['rank'];
    }
    else
    {
        $arr[$i]['rank'] = $i + 1;
    }
    $prev = $sub_arr;
}