Keep duplicate keys when fill keys for multilevel arrays

im trying to fill values from array1 as keys for array2 but i got problem if keys are duplicate:

$arr1 = array(
    array(0 => "1", 1 => "1"),
    array(0 => "2", 1 => "2"),
);
$arr2 = array(
    array(0 => "a", 1 => "b"),
    array(0 => "c", 1 => "d"),
);

$result = [];

for ($i = 0; $i < count($arr1); $i++)
{
    $result[$i] = array_combine($arr1[$i], $arr2[$i]);
}

result i got:

$result = array(
    array(1 => "b"),
    array(2 => "d"),
);

I need it like this:

$result = array(
    array(1 => "a", 1 => "b"),
    array(2 => "c", 2 => "d"),
);

Modified output I want now: (after looking all comments/answer)

array (
  0 => 
  array (
    0 => array(
       0 => '1',
       1 => 'a',
            ),
    1 => array(
       0 => '1',
       1 => 'b',
            ),

  ),
  1 => 
  array (
    0 => array(
       0 => '1',
       1 => 'c',
            ),
    1 => array(
       0 => '1',
       1 => 'd',
            ),

  ),
);

Thank you!

Answer

1st solution : You cannot get what you want as same indexes in php array got over-write:https://3v4l.org/r934K

What best possible you can get is:

$result = [];

foreach($arr1 as $key=>$value){
   $result[array_unique($value)[0]] = $arr2[$key];
}

Output: https://3v4l.org/DfPU3

2nd soultion : For the output what you want, you need to apply one more foreach()

$result = [];

foreach($arr1 as $key=>$value){
   foreach($value as $k=>$val){
       $result[$key][$k] = [$val,$arr2[$key][$k]];
   }
}

print_r($result);

Output : https://3v4l.org/u8JmX