多个数组形成另一个数组的有关问题

多个数组形成另一个数组的问题
程序中形成了以下的数组（程序的中的key是动态的，这里写死了）

Array
(
    [Category] => TOTAL
    [January2014_Number_stores] => 0
    [February2014_Number_stores] => 0
    [March2014_Number_stores] => 0
)

又有数组

Array
(
    [January2014_Number_stores] => 155
    [February2014_Number_stores] => 155
    [March2014_Number_stores] => 155
)
Array
(
    [January2014_Number_stores] => 126
    [February2014_Number_stores] => 126
    [March2014_Number_stores] => 126
)
Array
(
    [January2014_Number_stores] => 37
    [February2014_Number_stores] => 37
    [March2014_Number_stores] => 37
)
Array
(
    [January2014_Number_stores] => 9
    [February2014_Number_stores] => 9
    [March2014_Number_stores] => 9
)
Array
(
    [January2014_Number_stores] => 4
    [February2014_Number_stores] => 4
    [March2014_Number_stores] => 4
)

现在要把第二组中的数组中key值相同的相加求和后赋值给第一个数组，该怎么写？ 如果key值是动态有规律的该怎么写？
------解决方案--------------------

$a = array(
  'Category' => 'TOTAL',
  'January2014_Number_stores' => 0,
  'February2014_Number_stores' => 0,
  'March2014_Number_stores' => 0,
);

$b = array(
  array(
    'January2014_Number_stores' => 155,
    'February2014_Number_stores' => 155,
    'March2014_Number_stores' => 155,
  ),
  array(
    'January2014_Number_stores' => 126,
    'February2014_Number_stores' => 126,
    'March2014_Number_stores' => 126,
  ),
  array(
    'January2014_Number_stores' => 37,
    'February2014_Number_stores' => 37,
    'March2014_Number_stores' => 37,
  ),
  array(
    'January2014_Number_stores' => 9,
    'February2014_Number_stores' => 9,
    'March2014_Number_stores' => 9,
  ),
  array(
    'January2014_Number_stores' => 4,
    'February2014_Number_stores' => 4,
    'March2014_Number_stores' => 4,
  ),
);
foreach($b as $r) {
  foreach($r as $k=>$v) {
    if(! isset($a[$k])) $a[$k] = 0;
    $a[$k] += $v;
  }
}
print_r($a);

Array
(
[Category] => TOTAL
[January2014_Number_stores] => 331
[February2014_Number_stores] => 331
[March2014_Number_stores] => 331
)