Why does i get this magige : i get this error when i try to do 

mysqli_num_rows()

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given in C:\xampp\htdocs\php\search.php on line 13
There are no results matching your search

    $search = mysqli_real_escape_string($conn, $_POST['search']);
          $sql = "SELECT * FROM posts WHERE a_title LIKE '%$search%' OR a_text LIKE '%$search%' OR a_author LIKE '%$search%' OR a_date LIKE '%$search%";
          $result = mysqli_query($conn, $sql);
          $queryResult = mysqli_num_rows($result);

