コード
$arr = ["hoge" => 1, "piyo" => 2, "fuga" => 1];
$arr2 = ["hoge" => 1, "fuga" => 3, "hogehoge" => 0];
foreach ($arr2 as $key => $val) {
if (array_key_exists($key, $arr)) {
$arr[$key] = $arr[$key] + $val;
} else {
$arr[$key] = $val;
}
}
print_r($arr)
返り値
Array
(
[hoge] => 2
[piyo] => 2
[fuga] => 4
[hogehoge] => 0
)