php - 尝试获取非对象的属性/调用 bool 值上的成员函数bind_param()

Question

我知道这个问题已被问过很多次，但解决方案似乎对我不起作用。

我正在写一个简单的博客，我想创建一个存档部分，但我卡住了。这是我的一段代码，很麻烦:

            $month = $_GET['month'];
            $year = $_GET['year'];

            $from = date('Y-m-01 00:00:00', strtotime("$year-$month"));
            $to = date('Y-m-31 23:59:59', strtotime("$year-$month"));

            echo $from;
            echo $to;

            $sql = "SELECT * FROM posts WHERE date >= ".$from." AND date <= ".$to." ORDER BY date DESC";
            $stmt = $conn->query($sql);
            var_dump($stmt);

            if($stmt->num_rows > 0){
                while($row = $stmt->fetch_assoc()){

这段代码在 if 语句中给了我以下错误(尝试获取非对象的属性)。 var_dump() 返回 bool(false)。所以看起来查询是有问题的，但就我而言是没问题的。我查了一下，没有错别字，所有的名字也都是正确的。

我也尝试这样做:

            $month = $_GET['month'];
            $year = $_GET['year'];

            $from = date('Y-m-01 00:00:00', strtotime("$year-$month"));
            $to = date('Y-m-31 23:59:59', strtotime("$year-$month"));

            echo $from;
            echo $to;

            $sql = "SELECT * FROM posts WHERE date >= ".$from." AND date <= ".$to." ORDER BY date DESC";
            $stmt = $conn->prepare($sql);
            var_dump($stmt);
            $stmt->bind_param('ii', $from, $to);
            $stmt->execute();

但是它给了我一个不同的错误(调用 bool 值上的成员函数bind_param())，所以再次看来查询是一个问题。我真的不知道该如何处理这个问题。有什么建议吗？

更新:

                $month = $_GET['month'];
            $year = $_GET['year'];

            //set from and to dates
            $from = date('Y-m-01 00:00:00', strtotime("$year-$month"));
            $to = date('Y-m-31 23:59:59', strtotime("$year-$month"));

            echo $from;
            echo $to;

            $sql = "SELECT * FROM posts WHERE date >= ? AND date <= ? ORDER BY date DESC";
            $stmt = $conn->prepare($sql);
            //var_dump($stmt);
            $stmt->bind_param('ii', $from, $to);
            $stmt->execute();

            if($stmt->num_rows > 0){
                while($row = $stmt->fetch_assoc()){
                    $query = "SELECT * FROM comments WHERE postId=".$row['id'];
                    $comNumber = $conn->query($query);
                    $total = $comNumber->num_rows;


                    echo "<section class='post'>
                                <img class='postImage' src='img/".$row['id'].".png'>
                                <div class='postComment'>
                                    <div class='postCommentBubble'><img src='img/commentBubble.svg'></div>
                                    <div class='postCommentCount'>".$total." comments</div>";

                    echo "<div class='postDate'>".date("d F Y G:i", strtotime($row["date"]))."</div>";

                        if(isset($_SESSION['user']) && $_SESSION['privileges']==true){
                            echo "<a class='postDelete' href='delete-post.php?id=".$row["id"]."'><img src='img/garbage.svg'></a>";
                            echo "<a class='postEdit' href='edit-post.php?id=".$row["id"]."'><img src='img/pencil.svg'></a>";
                        }

                        echo "</div>
                                <header class='postTitle'><a href='post.php?id=".$row['id']."'>".$row['title']."</a></header>
                                <div class='postIntro'>".$row['intro']."</div>
                                <div class='postLinkContainer'><a class='postLink' href='post.php?id=".$row['id']."'>read more</a></div>
                            </section>
                            ";
                }
            }

Answer 1

请阅读此处:http://php.net/manual/en/mysqli.prepare.php准备好，如果失败，你会得到一个错误。因此你的错误。

问题是您的 SQL 需要使用 ? 代替变量名称，并且准备需要绑定(bind)数据。我相信你想要:

$sql = "SELECT * FROM posts WHERE date >= ? AND date <= ? ORDER BY date DESC";
$stmt->bind_param('ii', $from, $to);