当我遍历数据库表时，Foreach返回空

So I tried to loop through my database tabel with a foreach loop, but when I var_dump the function, it gives me an empty array. Here is the code:

   function getComment() {
    $db = connectDB();
    $sql = "SELECT `naam`, `title` FROM `comments` WHERE `naam`=:naam AND `title`=:title";
    $stmt = $db->prepare($sql);
    $stmt->bindParam(':naam', $naam);
    $stmt->bindParam(':title', $title);
    $stmt->execute();
    return $stmt->fetchAll();
}

foreach (getComment() as $value) {
    echo $value['naam'];
    echo $value['title'];
}

Variables $naam and $title are undefined in function scope. I suppose you want to pass'em as arguments:

function getComment($naam, $title) {
    $db = connectDB();
    $sql = "SELECT `naam`, `title` FROM `comments` WHERE `naam`=:naam AND `title`=:title";
    $stmt = $db->prepare($sql);
    $stmt->bindParam(':naam', $naam);
    $stmt->bindParam(':title', $title);
    $stmt->execute();
    return $stmt->fetchAll();
}

$naam = 'some naam';
$title = 'some title';
foreach (getComment($naam, $title) as $value) {
    echo $value['naam'];
    echo $value['title'];
}