Transpose and flatten two-dimensional indexed array where rows may not be of equal length

I would like to take an array like this and combine it into 1 single array.

array (size=2)
   0 => 
      array (size=10)
         0 => string '1' 
         1 => string 'a' 
         2 => string '3' 
         3 => string 'c' 
   1 => 
      array (size=5)
         0 => string '2'
         1 => string 'b'

However I want the array results to be interleaved.

So it would end up looking like

array
     0 => '1'
     1 => '2'
     2 => 'a'
     3 => 'b'
     4 => '3'
     5 => 'c'

I would like it so that it doesn't matter how many initial keys are passed in (this one has 2), it should work with 1, 2 or 5. Also, as you can see from my example the amount of elements most likely won't match.

Anyone know the best way to accomplish this?

$data = array(
    0 => array(
        0 => '1',
        1 => 'a',
        2 => '3',
        3 => 'c',
    ),
    1 => array(
        0 => '2',
        1 => 'b',
    ),
);

$newArray = array();
$mi = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
$mi->attachIterator(new ArrayIterator($data[0]));
$mi->attachIterator(new ArrayIterator($data[1]));
foreach($mi as $details) {
    $newArray = array_merge(
        $newArray,
        array_filter($details)
    );
}
var_dump($newArray);