Question

I have 2 arrays that I want to merge based on a key’s value in array 1. In the below example, I want the game_modes put into the games_list based on a key (id) in games_list.

Array 1 which is pulled from a table full of games:

$games_list = array(
  0 => array(
    'id' => 23,
    'name' => 'Call of Duty: Modern Warfare 3'
    ),
  2 => array(
    'id' => 1,
    'name' => 'Call of Duty: Black Ops'
    )
  );

Array 2 which is pulled from a table full of game modes:

$game_modes = array(
  0 => array(
    'id' => 1,
    'game_id' => 1,
    'description' => 'Capture the Flag'
    ),
  1 => array(
    'id' => 2,
    'game_id' => 1,
    'description => 'Domination'
    ),

  2 => array(
    'id' => 3,
    'game_id' => 23,
    'description' => 'Kill Confirmed'
    )
  );

I would like the result to be:

$games_list = array(
  0 => array(
    'id' => 23,
    'name' => 'Call of Duty: Modern Warfare 3'
    'modes' => array(
        array(
          'id' => 3,
          'game_id' => 23,
          'description' => 'Kill Confirmed'
          )
        )
    ),
  2 => array(
    'id' => 1,
    'name' => 'Call of Duty: Black Ops'
    'modes'=> array(
      0 => array(
        'id' => 1,
        'game_id' => 1,
        'description' => 'Capture the Flag'
        ),
      1 => array(
        'id' => 2,
        'game_id' => 1,
        'description => 'Domination'
        )
      )
    )
  );

Additional info, the site I’m working on currently has 71 games in its database and each game could have some arbitrary number of game modes.

Now, I could easily do a bunch of for loops and avoid this question all together. As of right now I don’t have ton of game modes entered into the database but I keep adding more all the time. Over time doing exponentially more loops all the time will eventually make the page load speed come to a crawl.

I have taken the time to place this data into memcache to make future calls quicker avoiding the loop.

I’ve never been good with array_map as I don’t quite understand how it works or if its even the right route.

Answer 1

Don’t you think query level solution would be better?
The lengthy way would be:

// array:  $game_modes;
// array:  $game_lists;

foreach ($game_modes as $gm=>$modes){
   if (isset($modes['game_id'])){
      foreach ($game_lists as $gl=>$lists){
         if ($lists['id'] == $modes['game_id']){
            $game_lists[$gl]['modes'][] = $modes;
            //break;
         }
      }
   }
}

Output Category : Summary

$query = 'SELECT 
                g.id, g.name_name,
                group_concat(gm.description) as descriptions
          FROM games as g
          LEFT JOIN games_modes as gm
               ON g.id = gm.game_id
          GROUP BY g.id';

Result:

  id |  name                     |  descriptions
------------------------------------------------------------
  1  |  Call of Duty: Black Ops  |  Capture the Flag, Domination

Output Category : Detail

$query = 'SELECT 
                g.id, g.name_name,
                gm.id, gm.description
          FROM games as g
          LEFT JOIN games_modes as gm
               ON g.id = gm.game_id
          ORDER BY g.id';

Result:

  id |  name                     |  id   |  description
----- --------------------------- ------- ------------------
  1  |  Call of Duty: Black Ops  |   1   |  Capture the Flag
  1  |  Call of Duty: Black Ops  |   2   |  Domination