PHP different filters on specific array names

My form returns an array that allows for duplicate form names (that is working just fine).

I'm not sure where I go next with sanitizing each based on there names. I'm allowing the user to build the form dynamically and thus will have variables named like $_POST['tutorial[smallImage_1]'], $_POST['tutorial[smallImage_2]'], etc.. (as seen in my example array below).

if ($_POST['tutorial']) {

   foreach ( $_POST['tutorial'] as $key=>$value ) {

       if ($_POST['tutorial[code]'] {
          $code = htmlentities($_POST['tutorial[code]']);
       }

    }
 }



[tutorial] => Array
    (
        [1] => Array
            (
                [subtitle] => subtitle text
            )

        [2] => Array
            (
                [paragraph] => paragraph text
            )

        [3] => Array
            (
                [largeImage_1] => Array
                    (
                        [0] => image.png
                    )

            )

        [4] => Array
            (
                [smallImage_1] => Array
                    (
                        [0] => image.png
                    )

            )

        [5] => Array
            (
                [code] => code text
            )

        [6] => Array
            (
                [smallImage_2] => array
                  (
                        [0] => image.png
                        [1] => image.png
                  )
            )