转换时我做错了什么[关闭]

Question

我需要将此 mysql 转换为 pdo 我尝试了以下操作，但我猜它是错误的，因为我没有显示任何结果。是的，这对你们中的一个人来说可能很容易，但 pdo 对我来说是个新闻，所以感谢你的帮助:)

实际代码

$rowperpage = 3;

            // counting total number of posts
            $allcount_query = "SELECT count(*) as allcount FROM posts";
            $allcount_result = mysql_query($allcount_query);
            $allcount_fetch = mysql_fetch_array($allcount_result);
            $allcount = $allcount_fetch['allcount'];

            // select first 3 posts
            $query = "select * from posts order by id asc limit 0,$rowperpage ";
            $result = mysql_query($query);

            while($row = mysql_fetch_array($result)){

                $id = $row['id'];
                $title = $row['title'];
                $content = $row['content'];
                $shortcontent = substr($content, 0, 160)."...";
                $link = $row['link'];

            ?>
                <!-- Post -->
                <div class="post" id="post_<?php echo $id; ?>">
                    <h1><?php echo $title; ?></h1>
                    <p>
                        <?php echo $shortcontent; ?>
                    </p>
                    <a href="<?php echo $link; ?>" class="more" target="_blank">More</a>
                </div>

            <?php
            }
            ?>

我尝试了什么

 $rowperpage = 3;

        // counting total number of posts
        //$allcount_query = "SELECT count(*) as allcount FROM posts";
        //$allcount_result = mysql_query($allcount_query);

        $query = "SELECT count(*) FROM posts";
        $stmt = $db->prepare($query);       



        $allcount_fetch = $stmt->fetch(PDO::FETCH_ASSOC);
        $allcount = $stmt->fetchColumn();

        // select first 3 posts
        //$query = "select * from posts order by id asc limit 0,$rowperpage ";
        //$result = mysql_query($query);

        $qry = "select * from posts order by id asc limit 0,$rowperpage ";
        $stm = $db->prepare($qry);  

        while($row = $stm->fetch(PDO::FETCH_ASSOC)){

            $id = $row['id'];
            $title = $row['title'];
            $content = $row['content'];
            $shortcontent = substr($content, 0, 160)."...";
            $link = $row['link'];

有人可以展示正确的方法吗？

Answer 1

prepare() 与execute() 一起使用

准备好的语句基本上是这样工作的：

1. 准备：创建一个 SQL 语句模板并将其发送到 数据库。某些值未指定，称为参数 （标记为“？”）。示例：

   INSERT INTO mtTable VALUES(?, ?, ?)

2. 数据库解析、编译并执行查询优化 SQL 语句模板，并存储结果而不执行 它

3. 执行：稍后，应用程序将值绑定到 参数，然后数据库执行该语句。应用程序 可以根据需要使用不同的语句多次执行该语句 价值观

试试下面的代码

<?php

$db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

$rowperpage = 3;
$offset     = 0;

// counting total number of posts
$query = "SELECT count(id) AS allcount  FROM posts";
$stmt  = $db->query($query)->fetchColumn();

/******** The ABOVE QUERY LOOKS POINTLESS TO ME AS YOU NOT USING THE RESULTS FROM THAT QUERY*/

// select first 3 posts

$qry = "SELECT * FROM posts ORDER BY id ASC LIMIT ?,? ";
$stm = $db->prepare($qry);
$stm->execute(array($offset,$rowperpage));
$results = $stm->fetchall(PDO::FETCH_ASSOC);

if (count($results) > 0) {

    foreach ($results as $row) {

        $id           = $row['id'];
        $title        = $row['title'];
        $content      = $row['content'];
        $shortcontent = substr($content, 0, 160) . "...";
        $link         = $row['link'];

    }
} else {

    echo "No records found";
}
?>