SELECT count(*) FROM blog_posts WHERE category = 'hot_stuff' and published <= NOW();

$myCategory = 'hot_stuff';
    $myTable = 'blog_posts';

    $sql = "SELECT count(*) FROM {$myTable} WHERE category = '{$myCategory}' and published <= NOW();";

    $rowCount = $db->query($sql);
    echo $rowCount;

$pdo = new PDO($dsn, $user, $password);

$stmt = $pdo->prepare("SELECT COUNT(*) FROM your_table
                       WHERE category = ? AND published  <= CURDATE()");

$stmt->execute([$category]);

echo $stmt->fetchColumn();