Combinando resultados de duas tabelas em JSON

$result_w = $conn->query("SELECT * FROM words;");
$results_w = $result_w->fetch_all(MYSQLI_ASSOC);

$words_per_paragraph = [];
foreach($results_w as $key => $row) {
    $words_per_paragraph[$row['paragraph_no']][] = $row;
}

$result_p = $conn->query("SELECT * FROM paragraph;");
$results_p = $result_p->fetch_all(MYSQLI_ASSOC);

$data = [];
foreach($results_p as $key => $row) {
    $p_no = $row['paragraph_no'];
    $words = [];
    if(array_key_exists($p_no, $words_per_paragraph)) {
        $words = $words_per_paragraph[$p_no];
    }
    $data[$p_no] = [
        'words' => $words,
        'paragraph' => $row
    ];
}

{
   "1":{
      "words":{
         "id":"4",
         "book_no":"1",
         "paragraph_no":"1",
         "word_no":"4",
         "word":"you"
      },
      "paragraph":{
         "id":"1",
         "book_no":"1",
         "paragraph_no":"1",
         "paragraph":"hello how are you"
      }
   },
   "2":{
      "words":[

      ],
      "paragraph":{
         "id":"3",
         "book_no":"1",
         "paragraph_no":"2",
         "paragraph":"I'm fine and you?"
      }
   }
}