How to conver string to int in implode combinate with array_filter and array_map

How can i remove text from values ? i like values of array to be numbers only.

        $arr = Array(
            '39' => Array(
                    '0' => '307'
                    ),
            '42' => Array(
                    '0' => '329ds',
                    '1' => '300'
                    )
               );

$result = implode(",", array_filter(array_map(function($v){
  return implode(",", array_filter($v));
}, $arr)));

echo $result;

//result: 307,329ds,300

i tried to add (int) on implode() and its working but returning only 2 numbers instead of 3 numbers

            $arr = Array(
            '39' => Array(
                    '0' => '307'
                    ),
            '42' => Array(
                    '0' => '329ds',
                    '1' => '300'
                    )
               );

$result = implode(",", array_filter(array_map(function($v){
  return (int)implode(",", array_filter($v));
}, $arr)));

echo $result;

//result: 307,329