Question

I have 2 arrays $list and $list2:

$list:

Array
(
[0] => Array
    (
        [team] => 14
        [team_points] => 3
        [team_occurrences] => 2
    )

[1] => Array
    (
        [team] => 1
        [team_points] => 3
        [team_occurrences] => 2
    )

[2] => Array
    (
        [team] => 5
        [team_points] => 1
        [team_occurrences] => 1
    )

[3] => Array
    (
        [team] => 13
        [team_points] => 1
        [team_occurrences] => 1
    )

[4] => Array
    (
        [team] => 7
        [team_points] => 0
        [team_occurrences] => 1
    )

[5] => Array
    (
        [team] => 2
        [team_points] => 0
        [team_occurrences] => 3
    )

 )

$list2:

Array
(
    [0] => Array
        (
            [team] => 20
            [team_points] => 7
            [team_occurrences] => 3
        )

    [1] => Array
        (
            [team] => 10
            [team_points] => 3
            [team_occurrences] => 1
        )

    [2] => Array
        (
            [team] => 14
            [team_points] => 3
            [team_occurrences] => 1
        )

    [3] => Array
        (
            [team] => 13
            [team_points] => 3
            [team_occurrences] => 1
        )

    [4] => Array
        (
            [team] => 19
            [team_points] => 3
            [team_occurrences] => 1
        )

    [5] => Array
        (
            [team] => 17
            [team_points] => 1
            [team_occurrences] => 1
        )

    [6] => Array
        (
            [team] => 11
            [team_points] => 0
            [team_occurrences] => 1
        )

    [7] => Array
        (
            [team] => 15
            [team_points] => 0
            [team_occurrences] => 1
        )

)

As you can see the columns are the same in both arrays (team, team_points, team_occurrences)

Now, I would like to merge these two arrays into array called $list_all

The problem with the merge is that standard merge I have tried

array_merge($list,$list2);

just add them together.

However, What I need is to count same teams e.g. [team] => 14 and [team] => 13 are in both arrays (in $list and $list2) , so, therefore I need to sum team_points column value from $list with and team_points column value from $list2 if the team is identical. The same for team_occurrences column.

So e.g.

New array will not look like this:

Array
(
[0] => Array // from $list
    (
        [team] => 14
        [team_points] => 3
        [team_occurrences] => 2
    )

[1] => Array // from $list2
    (
        [team] => 14
        [team_points] => 3
        [team_occurrences] => 1
    )

[3] => Array // from $list
    (
        [team] => 13
        [team_points] => 1
        [team_occurrences] => 1
    )

[4] => Array // from $list2
    (
        [team] => 13
        [team_points] => 3
        [team_occurrences] => 1
    )

But I need that it will look like this:

Array
(
[0] => Array 
    (
        [team] => 14
        [team_points] => 6
        [team_occurrences] => 3
    )

[1] => Array 
    (
        [team] => 13
        [team_points] => 4
        [team_occurrences] => 2
    )

After the merge I would like to sort the result array using usort() or maybe some better function by team_points DESC (from highest value to the lowest).

Thanks in advance for any advice.

Answer 1

Iterate over the first list, creating a new array whose keys are the team numbers. Then iterating over the second array, if the team already exists, add and otherwise, append.

$combined = array();
// First loop creates array keys in $combined array
// based on team numbers
foreach($list as $initial) {
  $combined[$initial['team']] = $initial; 
}

// Second loop looks at $list2 and either adds to values
// if the team key already exists, or just adds the 
// whole subarray on if it doesn't.
foreach($list2 as $secondary) {
  // If it was in the first, append to it.
  if (isset($combined[$secondary['team']])) {
    $combined[$secondary['team']]['team_points'] += $secondary['team_points'];
    $combined[$secondary['team']]['team_occurrences'] += $secondary['team_occurrences'];
  }
  // Otherwise, just add it to the array
  else {
    $combined[$secondary['team']] = $secondary;
  }
}

// Then sort the combined array with usort() into descending order by points
// Anonymous callback function is PHP 5.3+. Needs to be a string value of a named function
// for PHP < 5.3
usort($combined, function($a, $b) {
  if ($a['team_points'] === $b['team_points']) {
     return 0;
  }
  else {
     return $a['team_points'] < $b['team_points'] ? 1 : -1;
  }
});

Note: The above produces an output array keyed by team number. If you really just want ascending numeric keys, call array_values() on it:

// Strip off the team number keys and just use ascending numbers
$combined = array_values($combined);

Edit Fixed a few missing ] above…