July 4, 2013
How to merge array and preserve keys?
Joe’s Question:
I have two arrays:
$array1 = array('a' => 1, 'b' => 2, 'c' => 3);
$array2 = array('d' => 4, 'e' => 5, 'f' => 6, 'a' => 'new value', '123' => 456);
I want to merge them and keep the keys and the order and not re-index!!
How to get like this?
Array
(
[a] => new value
[b] => 2
[c] => 3
[d] => 4
[e] => 5
[f] => 6
[123] => 456
)
I try to array_merge() but it will not be preserved the keys:
print_r(array_merge($array1, $array2));
Array
(
[a] => 'new value'
[b] => 2
[c] => 3
[d] => 4
[e] => 5
[f] => 6
[0] => 456
)
I try to the union operator but it will not overwriting that element:
print_r($array1 + $array2);
Array
(
[a] => 1 <-- not overwriting
[b] => 2
[c] => 3
[d] => 4
[e] => 5
[f] => 6
[123] => 456
)
I try to swapped place but the order is wrong, not my need:
print_r($array2 + $array1);
Array
(
[d] => 4
[e] => 5
[f] => 6
[a] => new value
[123] => 456
[b] => 2
[c] => 3
)
I dont want to use a loop, is there a way for high performance?
You’re looking for array_replace():
$array1 = array('a' => 1, 'b' => 2, 'c' => 3);
$array2 = array('d' => 4, 'e' => 5, 'f' => 6, 'a' => 'new value', '123' => 456);
print_r(array_replace($array1, $array2));
Available since PHP 5.3.
Update
You can also use the union array operator; it works for older versions and might actually be faster too:
print_r($array2 + $array1);
