警告:mysqli_query()期望参数1为mysqli,null为null

Question

我正在尝试构建一个简单的自定义CMS,但我收到一个错误:

警告:mysqli_query()期望参数1为MySQLi,null为null

为什么我收到此错误？我的所有代码都已经是MySQLi,我使用的是两个参数,而不是一个.

$con=mysqli_connect("localhost","xxxx","xxxx","xxxxx");

//check connection
if (mysqli_connect_errno($con))
{
    echo "Failed to connect to MySQL:" . mysqli_connect_error();
}

function getPosts() {
    $query = mysqli_query($con,"SELECT * FROM Blog");
    while($row = mysqli_fetch_array($query))
    {
        echo "<div class=\"blogsnippet\">";
        echo "<h4>" . $row['Title'] . "</h4>" . $row['SubHeading'];
        echo "</div>";
    }
}

Answer 1

正如评论中所提到的,这是一个范围问题.具体而言,$con不在您的getPosts职能范围内.

您应该将连接对象作为依赖项传递,例如

function getPosts(mysqli $con) {
    // etc

如果连接失败,我还强烈建议暂停执行.这样的事情应该足够了

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); // throw exceptions
$con=mysqli_connect("localhost","xxxx","xxxx","xxxxx");

getPosts($con);

Answer 2

在你的$ con上使用全局范围并将其放在你的getPosts()函数中.

function getPosts() {
global $con;
$query = mysqli_query($con,"SELECT * FROM Blog");
while($row = mysqli_fetch_array($query))
    {
        echo "<div class=\"blogsnippet\">";
        echo "<h4>" . $row['Title'] . "</h4>" . $row['SubHeading'];
        echo "</div>";
    }
}