$array = array_merge_recursive($array1, $array2);
or make your own function (it may be faster)
function my_array_merge(&$array1, &$array2) {
$result = Array();
foreach($array1 as $key => &$value) {
$result[$key] = array_merge($value, $array2[$key]);
}
return $result;
}
$array = my_array_merge($array1, array2);
print_r($array);