PHP MySQLi 预处理语句在绑定不同参数时给出相同的结果

Question

我正在尝试制作一个 class，我可以用它来显示我的 5 个最新帖子和 4 个最受欢迎的帖子。我正在使用准备好的语句执行此操作，使 ORDER BY 语句保持打开状态以包含两个不同的参数。

问题是，当我运行这两个时，我得到相同的结果（帖子的顺序相同）。我运行在首页的代码是这样的：

<?php
    $test = new SideBar();
    echo $test->recent();
    echo $test->popular(); // returns the same as recent() for some reason
?>

这是 class:

class SideBar
{
    // Storing the names of the database table columns
    private $id = 'n';
    private $rating = 'mean';
    private $stmt;
    private $result;

    public function __construct()
    {
        global $mysqli;
        $this->stmt = $mysqli->prepare("SELECT n,title,date
                                        FROM claims
                                        WHERE active = 1 
                                        ORDER BY ? DESC
                                        LIMIT 5");
    }

    public function recent()
    {
        $this->result = "";
        return $this->build($this->id);
    }

    public function popular()
    {   
        $this->result = "";
        return $this->build($this->rating);
    }

    private function build($order)
    {
        $this->stmt->bind_param('s',$order);
        $this->stmt->execute();
        $this->stmt->bind_result($n, $title, $date);
        while($this->stmt->fetch())
        {
        $this->result .= '<a href="[mydomain]?id='.$n.'">';
        $this->result .= $title.' '.$date;
        $this->result .= "</a>\n";
        }
        return $this->result;
    }

    public function __destruct()
    {
        $this->stmt->close();
    }
}

Answer 1

显然您不能将列名绑定到 ORDER BY 子句。相反，您可以在 recent 和 popular 函数中形成必要的查询，并将 prepare pdo 语句移动到 build 函数中。以下是修改：

public function __construct()
    {
    }

    public function recent()
    {
        $this->result = "";
        $q="SELECT n,title,date
                                        FROM claims
                                        WHERE active = 1 
                                        ORDER BY id DESC
                                        LIMIT 5"
        return $this->build($q);
    }

    public function popular()
    {   
        $this->result = "";
        $q="SELECT n,title,date
                                        FROM claims
                                        WHERE active = 1 
                                        ORDER BY mean DESC
                                        LIMIT 5"
        return $this->build($q);
    }

    private function build($query)
    {
        global $mysqli;
        $stmt = $mysqli->prepare($query)
        $stmt->execute();
        $stmt->bind_result($n, $title, $date);
        while($stmt->fetch())
        {
        $this->result .= '<a href="[mydomain]?id='.$n.'">';
        $this->result .= $title.' '.$date;
        $this->result .= "</a>\n";
        }
        return $this->result;
    }

PHP MySQLi 预处理语句在绑定不同参数时给出相同的结果

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