How to check for the existence of a record in the database in 1C Bitrix?

Question

1C-Bitrix

Greetings. Guys, tell me why the text from the $disp variable is displayed immediately, but in fact the check works. The same design but works in a normal document. I use this code in Bitrix.

<?
$pol = $_POST['course'];
$gr = $_POST['gr'];
$disp = "В этом году для Вашего года рождения нет диспансеризации.";
$my = $DB->Query("SELECT * FROM b_dispp_2018 WHERE gr='$gr' && pol='$pol'");
$result = $my->Fetch();
        if ($result)  {
echo '<h2 style="color:green">' . $result['inf'] . '</h2>';
    }
    else 
  {
    echo $disp;
  }

?>

Answer 1

1) Read about sql injections. Example
2) If I were you, I would avoid using $DB->Query for queries. It's better to use D7 ORM instead . You describe the table with a class, and then use the data selections via getList or Query if you need a specific query.
Well, as already said, you need to check something more specific. From your description, it is not at all clear what you are trying to do.

Answer 2

Check $result more specifically, it's not Javascript for you.