Bagaimana Menjumlahkan Nilai Kunci Dikongsi Apabila Menggabungkan Berbilang Tatasusunan Bersekutu?

<code class="php">$sums = array();
foreach (array_keys($a1 + $a2) as $key) {
    $sums[$key] = (isset($a1[$key]) ? $a1[$key] : 0) + (isset($a2[$key]) ? $a2[$key] : 0);
}</code>

<code class="php">$keys = array_fill_keys(array_keys($a1 + $a2), 0);
$sums = array_map(function ($a1, $a2) { return $a1 + $a2; }, array_merge($keys, $a1), array_merge($keys, $a2));</code>

<code class="php">$sums = array_fill_keys(array_keys($a1 + $a2), 0);
array_walk($sums, function (&amp;$value, $key, $arrs) { $value = @($arrs[0][$key] + $arrs[1][$key]); }, array($a1, $a2));</code>

<code class="php">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;
}</code>