答案 0 :(得分：0)
这可能会指向正确的方向：
if (isset($_POST['card_genre'])) {
$query = "SELECT card_catalog.card_name, card_catalog.card_label, card_genre.genre_id FROM card_catalog, card_genre WHERE card_genre.genre_id = ?";
$stmt = mysqli_prepare($conn, $query);
$stmt->bind_param('s', $_POST['card_genre']);
$stmt->execute();
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
echo $row['card_name']." - ".$row['genre_id'];
echo "<br />";
}
} else {
$query = "SELECT card_catalog.card_name, card_catalog.card_label, card_genre.genre_id FROM card_catalog, card_genre";
$result = mysqli_query($conn, $query) or die(mysqli_error($conn));
while ($row = mysqli_fetch_array($result)) {
echo $row['card_name']." - ".$row['genre_id'];
echo "<br />";
}
}