MySQLi准备语句查询问题

Question

我对MySQLi准备好的语句比较新，并且遇到了错误。拿这个代码：

$user = 'admin';
$pass = 'admin';

if ($stmt = $mysqli->query("SELECT * FROM members WHERE username='$user' AND     password='$pass'"))
{
echo $stmt->num_rows;
}

这将显示“1”，因为它应该。

下一段代码虽然返回“0”：

$user = 'admin';
$pass = 'admin';

if ($stmt = $mysqli->prepare("SELECT * FROM members WHERE username=? AND password=?"))
{
$stmt->bind_param("ss", $user, $pass);
$stmt->execute();
echo $stmt->num_rows;
}

任何想法为什么？

Answer 1

您需要在获得行数之前调用store_result()

$user = 'admin';
$pass = 'admin';


if ($stmt = $mysqli->prepare("SELECT * FROM members WHERE username=? AND password=?"))
{
$stmt->bind_param("ss", $user, $pass);
$stmt->execute();
$stmt->store_result();  // add this line
echo $stmt->num_rows;
}