Convert 3d array into an associative array of unique values and sum their related values

Assuming you can collect all your arrays into one i.e. :

$arrays = array($array1,$array2,....,$arrayn);

then

$grouping = array();

foreach($arrays AS $array)
{
   foreach($array['winners'] AS $k=>$v)
   {
      //check if the array key is a number, will contain a team, and if that
      //them is not alreay listed
      if(is_numeric($k) && !array_key_exists($v,$grouping))
         $grouping[$v] = 0;
      //sum the prize to the team's sum
      $grouping[$v] += intval($array['winners']['prizeTotal']);
   }
}
//the following is just for debugging
print_r($grouping);

this should produce something like:

$grouping[TEAM #1] = 200
$grouping[TEAM #2] = 90
$grouping[CROTCH SNIFFER] = 200
...

You need to make a new array to hold your results, then for each of your existing arrays, check if you're already processed one for that team

If you have, then simply add the prizeTotal to the prizeTotal stored in your new array's entry for that team.

If not, simply add the team's entry to your new array.

To generate an associative array of unique teams and their cumulative scores:

1. Use a loop to access each data subset
2. Use extract() to conveniently access the winner and prizeTotal data as individual variables.
3. Loop the winner elements
4. Declare the winner as the key in the result array and the value should be the prizeTotal plus the cached value (or zero if there is no cached value).

Code: (Demo)

$result = [];
foreach ($array as $set) {
    extract($set);
    foreach ($winners as $winner) {
        $result[$winner] = ($result[$winner] ?? 0) + $prizeTotal;
    }
}
var_export($result);

Instead of calling extract(), "array destructuring" can create individual variables as well.

$result = [];
foreach ($array as ['winners' => $winners, 'prizeTotal' => $prizeTotal]) {
    foreach ($winners as $winner) {
        $result[$winner] = ($result[$winner] ?? 0) + $prizeTotal;
    }
}
var_export($result);

I have made a function that imitates mysql SUM() and GROUP BY. I hope it will fit your needs:

           $in_a = array(
                array("a" => 0,"b"=>0,"s"=> 1),
                array("a" => 0,"b"=>0,"s"=> 2),
                array("a" => 1,"b"=>1,"s"=> 1),
                array("a" => 0,"b"=>1,"s"=> 1),
                array("a" => 0,"b"=>1,"s"=> 1),
                array("a" => 1,"b"=>0,"s"=> 1),         
                array("a" => 0,"b"=>1,"s"=> 1),         
                array("a" => 1,"b"=>1,"s"=> 1),         
                array("a" => 1,"b"=>0,"s"=> 1),         
            );//input array exaple
            $group_by_a = array("a","b");//input array will be grouped by these
            $sum_a = array("s"); //'s' values of input will be summed
            $out_a = array(); //this is the output array

            foreach($in_a as $in_i => $in)
            {
                $add = false;
                foreach($out_a as $out_i => $out)
                {
                    $add = true;
                    foreach($group_by_a as $group_by)
                        if($in[$group_by] != $out[$group_by])
                        {
                            $add = false; 
                            break;
                        }                   
                    if($add)
                    {
                        foreach($sum_a as $sum)
                            $out_a[$out_i][$sum] += $in[$sum];  
                        break;
                    }
                }
                if(!$add)
                {
                    foreach($group_by_a as $group_by)
                        $out_a[$in_i][$group_by] = $in[$group_by];
                    foreach($sum_a as $sum)
                        $out_a[$in_i][$sum] = $in[$sum];                    
                }                   
            }

the result:

Array
(
    [0] => Array
        (
            [a] => 0
            [b] => 0
            [s] => 3
        )

    [2] => Array
        (
            [a] => 1
            [b] => 1
            [s] => 2
        )

    [3] => Array
        (
            [a] => 0
            [b] => 1
            [s] => 3
        )

    [5] => Array
        (
            [a] => 1
            [b] => 0
            [s] => 2
        )

)