How can I merge PHP arrays? - php

Question

I have two arrays of animals (for example).
$array = array(
array(
'id' => 1,
'name' => 'Cat',
),
array(
'id' => 2,
'name' => 'Mouse',
)
);
$array2 = array(
array(
'id' => 2,
'age' => 321,
),
array(
'id' => 1,
'age' => 123,
)
);
How can I merge the two arrays into one by the ID?

Answer 1

#Andy
http://se.php.net/array_merge
That was my first thought but it doesn't quite work - however array_merge_recursive might work - too lazy to check right now.

Answer 2

This does what Erik suggested (id no. as array key) and merges vlaues in $array2 to $results.
$results = array();
foreach($array as $subarray)
{
$results[$subarray['id']] = array('name' => $subarray['name']);
}
foreach($array2 as $subarray)
{
if(array_key_exists($subarray['id'], $results))
{
// Loop through $subarray would go here if you have extra
$results[$subarray['id']]['age'] = $subarray['age'];
}
}

Answer 3

First off, why don't you use the ID as the index (or key, in the mapping-style array that php arrays are imo)?
$array = array(
1 => array(
'name' => 'Cat',
),
2 => array(
'name' => 'Mouse',
)
);
after that you'll have to foreach through one array, performing array_merge on the items of the other:
foreach($array2 as $key=>$value) {
if(!is_array($array[$key])) $array[$key] = $value;
else $array[$key] = array_merge($array[key], $value);
}
Something like that at least. Perhaps there's a better solution?

Answer 4

<?php
$a = array('a' => '1', 'b' => array('t' => '4', 'g' => array('e' => '8')));
$b = array('c' => '3', 'b' => array('0' => '4', 'g' => array('h' => '5', 'v' => '9')));
$c = array_merge_recursive($a, $b);
print_r($c);
?>
array_merge_recursive — Merge two or more arrays recursively
outputs:
Array
(
[a] => 1
[b] => Array
(
[t] => 4
[g] => Array
(
[e] => 8
[h] => 5
[v] => 9
)
[0] => 4
)
[c] => 3
)

Answer 5

#Andy
I've already looked at that and didn't see how it can help merge multidimensional arrays. Maybe you could give an example.
#kevin
That is probably what I will need to do as I think the code below will be very slow.
The actual code is a bit different because I'm using ADOdb (and ODBC for the other query) but I'll make it work and post my own answer.
This works, however I think it will be very slow as it goes through the second loop every time:
foreach($array as &$animal)
{
foreach($array2 as $animal2)
{
if($animal['id'] === $animal2['id'])
{
$animal = array_merge($animal, $animal2);
break;
}
}
}

Answer 6

foreach ($array as $a)
$new_array[$a['id']]['name'] = $a['name'];
foreach ($array2 as $a)
$new_array[$a['id']]['age'] = $a['age'];
and this is result:
[1] => Array
(
[name] => Cat
[age] => 123
)
[2] => Array
(
[name] => Mouse
[age] => 321
)

Answer 7

<?php
$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
print_r($result);
?>

Answer 8

With PHP 5.3 you can do this sort of merge with array_replace_recursive()
http://www.php.net/manual/en/function.array-replace-recursive.php
You're resultant array should look like:
Array (
[0] => Array
(
[id] => 2
[name] => Cat
[age] => 321
)
[1] => Array
(
[id] => 1
[name] => Mouse
[age] => 123
)
)
Which is what I think you wanted as a result.

Answer 9

I would rather prefer array_splice over array_merge because of its performance issues, my solution would be:
<?php
array_splice($array1,count($array1),0,$array2);
?>

Answer 10

$new = array();
foreach ($array as $arr) {
$match = false;
foreach ($array2 as $arr2) {
if ($arr['id'] == $arr2['id']) {
$match = true;
$new[] = array_merge($arr, $arr2);
break;
}
}
if ( !$match ) $new[] = $arr;
}