Это может помочь вам.
function recursiveSum($array, $keyToSearch) {
$total = 0;
foreach($array as $key => $value) {
if(is_array($value)) {
$total += recursiveSum($value, $keyToSearch);
}
else if($key == $keyToSearch) {
$total += $value;
}
}
return $total;
}
$total = recursiveSum($array, "test");