注意：创建帖子时未定义的变量

Question

我是PHP和MySQL的新手，我只是想不出这个。我在论坛周围搜索过但没有找到答案。问题是我删除了CMS中的所有帖子，它显示以下错误：

我犯了错误？

提前感谢您的帮助！

我的源代码：

<?php

    $query = "SELECT * FROM posts";
    $select_posts = mysqli_query($connection, $query);

    while($row = mysqli_fetch_assoc($select_posts)) {
        $post_id = $row['post_id'];
        $post_author = $row['post_author'];
        $post_title = $row['post_title'];
        $post_category_id = $row['post_category_id'];
        $post_status = $row['post_status'];
        $post_image = $row['post_image'];
        $post_tags = $row['post_tags'];
        $post_comment_count = $row['post_comment_count'];
        $post_date = $row['post_date'];
    }

    echo "<tr>";
    echo "<td>$post_id</td>";
    echo "<td>$post_author</td>";
    echo "<td>$post_title</td>";

    $query = "SELECT * FROM categories WHERE cat_id = {$post_category_id} ";
    $select_categories_id = mysqli_query($connection, $query);

    while($row = mysqli_fetch_assoc($select_categories_id)) {
        $cat_id = $row['cat_id'];
        $cat_title = $row['cat_title'];

        echo "<td>{$cat_title}</td>";

    }

    echo "<td>$post_status</td>";
    echo "<td><img src='../images/$post_image' width='150' height='50'></td>";
    echo "<td>$post_tags</td>";
    echo "<td>$post_comment_count</td>";
    echo "<td>$post_date</td>";
    echo "<td><a href='posts.php?source=edit_post&p_id={$post_id}'>Edit</a></td>";
    echo "<td><a href='posts.php?delete={$post_id}'>Delete</a></td>";
    echo "</tr>";

    ?>

Answer 1

如果您删除了所有记录，那么在尝试将它们回显到屏幕之前，您应该进行逻辑测试以检查是否有一些记录。

<?php

    $query = "SELECT * FROM posts";
    $select_posts = mysqli_query( $connection, $query );



    /* check there are records in recordset */
    if( mysqli_num_rows( $select_posts ) > 0 ) {

        while($row = mysqli_fetch_assoc($select_posts)) {
            $post_id = $row['post_id'];
            $post_author = $row['post_author'];
            $post_title = $row['post_title'];
            $post_category_id = $row['post_category_id'];
            $post_status = $row['post_status'];
            $post_image = $row['post_image'];
            $post_tags = $row['post_tags'];
            $post_comment_count = $row['post_comment_count'];
            $post_date = $row['post_date'];
        }

        echo "<tr>";
        echo "<td>$post_id</td>";
        echo "<td>$post_author</td>";
        echo "<td>$post_title</td>";

        $query = "SELECT * FROM categories WHERE cat_id = {$post_category_id} ";
        $select_categories_id = mysqli_query($connection, $query);

        while( $row = mysqli_fetch_assoc( $select_categories_id ) ) {
            $cat_id = $row['cat_id'];
            $cat_title = $row['cat_title'];

            echo "<td>{$cat_title}</td>";
        }

        echo "<td>$post_status</td>";
        echo "<td><img src='../images/$post_image' width='150' height='50'></td>";
        echo "<td>$post_tags</td>";
        echo "<td>$post_comment_count</td>";
        echo "<td>$post_date</td>";
        echo "<td><a href='posts.php?source=edit_post&p_id={$post_id}'>Edit</a></td>";
        echo "<td><a href='posts.php?delete={$post_id}'>Delete</a></td>";
        echo "</tr>";
    }
?>

Answer 2

您必须将整个代码放入while循环中，因为这取决于查询的结果。

<?php

    $query = "SELECT * FROM posts";
    $select_posts = mysqli_query($connection, $query);

    while($row = mysqli_fetch_assoc($select_posts)) {
        $post_id = $row['post_id'];
        $post_author = $row['post_author'];
        $post_title = $row['post_title'];
        $post_category_id = $row['post_category_id'];
        $post_status = $row['post_status'];
        $post_image = $row['post_image'];
        $post_tags = $row['post_tags'];
        $post_comment_count = $row['post_comment_count'];
        $post_date = $row['post_date'];


    echo "<tr>";
    echo "<td>$post_id</td>";
    echo "<td>$post_author</td>";
    echo "<td>$post_title</td>";

    $query = "SELECT * FROM categories WHERE cat_id = {$post_category_id} ";
    $select_categories_id = mysqli_query($connection, $query);

    while($row_inner = mysqli_fetch_assoc($select_categories_id)) {
        $cat_id = $row_inner['cat_id'];
        $cat_title = $row_inner['cat_title'];

        echo "<td>{$cat_title}</td>";

    }

    echo "<td>$post_status</td>";
    echo "<td><img src='../images/$post_image' width='150' height='50'></td>";
    echo "<td>$post_tags</td>";
    echo "<td>$post_comment_count</td>";
    echo "<td>$post_date</td>";
    echo "<td><a href='posts.php?source=edit_post&p_id={$post_id}'>Edit</a></td>";
    echo "<td><a href='posts.php?delete={$post_id}'>Delete</a></td>";
    echo "</tr>";
}
    ?>