PHP merging arrays based on specific array key - php

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

Answer 2

Try this to decrease looping
$cachearray = array();
foreach ($game_modes as $gm=>$modes){
if(array_key_exists($modes['game_id'],$cachearray))
{
$cachearray[$modes['game_id']]['modes'][] = $modes;
}
else
foreach ($games_list as $gl=>$lists){
if ($lists['id'] == $modes['game_id']){
$games_list[$gl]['modes'][] = $modes;
$cachearray[$lists['id']] = &$games_list[$gl];
break;
}
}
}
print_r($games_list);
It will be easier if you have $games_list array like this
$games_list = array(
23 => array(
'id' => 23,
'name' => 'Call of Duty: Modern Warfare 3'
),
1 => array(
'id' => 1,
'name' => 'Call of Duty: Black Ops'
)
);
And will more powerfull by using query

Answer 3

If you want to user array map, this code should be possible:
$ids = array_map(function($game) { return $game['id']; }, $games_list);
$id_mapping = array_flip($ids);
foreach($game_modes as $mode) {
if (array_key_exists($mode['game_id'], $id_mapping)) {
$games_list[$id_mapping[$mode['game_id']]]['modes'][] = $mode;
}
}
But I do not know whether this is faster than the two for loops.

Answer 4

try this:
$mode_map = array();
foreach($game_modes as $mode)
{
$game_id = $mode['game_id'];
if(!isset($mode_map[$game_id]))
{
$mode_map[$game_id] = array();
}
$mode_map[$game_id][] = $mode;
}
foreach($games_list as &$game)
{
$game_id = $game['id'];
if(isset($mode_map[$game_id]))
{
$game['modes'] = $mode_map[$game_id];
}
}
print_r($games_list);
result:
Array
(
[0] => Array
(
[id] => 23
[name] => Call of Duty: Modern Warfare 3
[modes] => Array
(
[0] => 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
)
)
)
)