php - 准备好的语句错误。新手问题

Question

我无法弄清楚这几行有什么问题：

    if  ( $stmt = $db->prepare('SELECT * FROM users WHERE username = ? LIMIT 1');
    $stmt->bind_param('s', $username);
    $stmt->execute();
    $stmt->store_result();
    $stmt->fetch();
    $stmt->num_rows == 1;
    )           

    {
    $errors[] = "Username is taken.";
    }

Answer 1

不知道你是如何得到你的其他代码的，但我认为你想要这样的东西：

$stmt = $db->prepare('SELECT * FROM users WHERE username = ? LIMIT 1');
$stmt->bind_param('s', $username);
$stmt->execute();
$stmt->bind_result($res);

if($stmt->num_rows == 1)
{
    $errors[] = "Username is taken.";
}

您的原始代码中也有不必要的提取

Answer 2

if($stmt = $db->prepare('SELECT * FROM users WHERE username = ? LIMIT 1'))
{
    $stmt->bind_param('s', $username);
    $stmt->execute();
    $stmt->store_result();
    if($stmt->num_rows > 0)
    {
        $errors[] = "Username $username is taken.";
    }
    $stmt->free_result();
    $stmt->close();
}