How to merge two arrays by summing the merged values [duplicate] - php

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Closed 11 years ago.
Possible Duplicate:
PHP: How to sum values of the array of the same key
I am looking for an array_merge() function that does NOT replace values, but ADDS them.
Example, this is the code I am trying:
echo "<pre>";
$a1 = array(
"a" => 2
,"b" => 0
,"c" => 5
);
$a2 = array(
"a" => 3
,"b" => 9
,"c" => 7
,"d" => 10
);
$a3 = array_merge($a1, $a2);
print_r($a3);
Sadly, this outputs this:
Array
(
[a] => 3
[b] => 9
[c] => 7
[d] => 10
)
I then tried, instead of array_merge, just simply adding the two arrays
$a3 = $a1 + $a2;
But this outputs
Array
(
[a] => 2
[b] => 0
[c] => 5
[d] => 10
)
What I truly want is to be able to pass as many arrays as needed, and then get their sum. So in my example, I want the output to be:
Array
(
[a] => 5
[b] => 9
[c] => 12
[d] => 10
)
Of course I can schlepp and build some function with many foreach etc, but am looking or a smarter, cleaner solution. Thanks for any pointers!

Answer 1

$sums = array();
foreach (array_keys($a1 + $a2) as $key) {
$sums[$key] = (isset($a1[$key]) ? $a1[$key] : 0) + (isset($a2[$key]) ? $a2[$key] : 0);
}
You could shorten this to the following using the error suppression operator, but it should be considered ugly:
$sums = array();
foreach (array_keys($a1 + $a2) as $key) {
$sums[$key] = #($a1[$key] + $a2[$key]);
}
Alternatively, some mapping:
$keys = array_fill_keys(array_keys($a1 + $a2), 0);
$sums = array_map(function ($a1, $a2) { return $a1 + $a2; }, array_merge($keys, $a1), array_merge($keys, $a2));
Or sort of a combination of both solutions:
$sums = array_fill_keys(array_keys($a1 + $a2), 0);
array_walk($sums, function (&$value, $key, $arrs) { $value = #($arrs[0][$key] + $arrs[1][$key]); }, array($a1, $a2));
I think these are concise enough to adapt one of them on the spot whenever needed, but to put it in terms of a function that accepts an unlimited number of arrays and sums them:
function array_sum_identical_keys() {
$arrays = func_get_args();
$keys = array_keys(array_reduce($arrays, function ($keys, $arr) { return $keys + $arr; }, array()));
$sums = array();
foreach ($keys as $key) {
$sums[$key] = array_reduce($arrays, function ($sum, $arr) use ($key) { return $sum + #$arr[$key]; });
}
return $sums;
}

Answer 2

My contribution:
function array_merge_numeric_values()
{
$arrays = func_get_args();
$merged = array();
foreach ($arrays as $array)
{
foreach ($array as $key => $value)
{
if ( ! is_numeric($value))
{
continue;
}
if ( ! isset($merged[$key]))
{
$merged[$key] = $value;
}
else
{
$merged[$key] += $value;
}
}
}
return $merged;
}
Pass as many arrays to it as you want. Feel free to add some more defense, ability to accept multidimensional arrays, or type checking.
Demo: http://codepad.org/JG6zwAap

Answer 3

its not so complicate
do something like:
$a3 = $a1;
foreach($a2 as $k => $v) {
if(array_key_exists($k, $a3)) {
$a3[$k] += $v;
} else {
$a3[$k] = $v;
}
}