require_once "../includes/db_connection.php";
require_once "../includes/functions.php";
global $user;
if (isset($_GET['user_id']) && isset($_GET['blog_id'])) {
    $query = "DELETE FROM blogs WHERE id = {$_GET['blog_id']} \n\t\t\tand subject_id = {$_GET['user_id']} LIMIT 1";
    $query_comment = "DELETE FROM comments WHERE blog_id = {$_GET['blog_id']}";
    $result = mysqli_query($connection, $query);
    $result_comments = mysqli_query($connection, $query_comment);
    if ($result && $result_comments) {
        redirect_to("show_user.php?id={$_GET['user_id']}");
    } else {
        // echo $id == null;
        echo "Blog Deletion failed";
    }
} else {
    if (isset($_GET['de'])) {
        $all_blogs = find_all_blogs_of_user("blogs", $_GET['user_id']);
        while ($blogs = mysqli_fetch_assoc($all_blogs)) {
            $query_1 = "DELETE FROM comments WHERE blog_id={$blogs["id"]}";
            $result_1 = mysqli_query($connection, $query_1);
        }
        $query = "DELETE FROM blogs WHERE subject_id={$_GET['user_id']}";
        $result = mysqli_query($connection, $query);
        if ($result && $result_1) {
            redirect_to("show_user.php?id={$_GET['user_id']}");
        } else {
            // echo $id == null;
            echo "Blogs Deletion failed";
        }
    }
}
<?php

require_once "../includes/db_connection.php";
require_once "../includes/functions.php";
global $user;
if (isset($_GET['id'])) {
    $id = $_GET['id'];
    //delete all comments that belongs to this user's every blog;
    $all_blogs = find_all_blogs_of_user("blogs", $id);
    while ($blogs = mysqli_fetch_assoc($all_blogs)) {
        $query_1 = "DELETE FROM comments WHERE blog_id={$blogs["id"]}";
        $result_1 = mysqli_query($connection, $query_1);
    }
    // delte all comments that this user wrote
    $query_2 = "DELETE FROM comments WHERE user_id={$id}";
    $result_2 = mysqli_query($connection, $query_2);
    $query_blogs = "DELETE FROM blogs WHERE subject_id = {$id}";
    $query = "DELETE FROM users WHERE id = {$id} LIMIT 1";
    $result = mysqli_query($connection, $query);
    $result_blogs = mysqli_query($connection, $query_blogs);
    if ($result) {
        redirect_to("manage_content.php");
    } else {
        // echo $id == null;
        echo "User Deletion failed";
    }
} else {
    if (isset($_GET['de'])) {
        $query = "Truncate table users";
        $result = mysqli_query($connection, $query);
        $query_1 = "Truncate table blogs";
function show_blogs_of_user($table, $id)
{
    $blogs_set = find_all_blogs_of_user($table, $id);
    // print_r(array_values($blogs_set));
    $output = "<table id=\"t023\">";
    $output .= "<tr>";
    $output .= "<th>Title</th>";
    $output .= "<th>View Counts</th>";
    $output .= "<th>Create Time</th>";
    $output .= "<th>Update Time</th>";
    $output .= "<th>Content</th>";
    $output .= "</tr>";
    while ($blogs = mysqli_fetch_assoc($blogs_set)) {
        $output .= "<tr>";
        $output .= "<td>{$blogs["title"]}</td>";
        $output .= "<td>{$blogs["view_counts"]}</td>";
        $output .= "<td>{$blogs["create_time"]}</td>";
        $output .= "<td>{$blogs["update_time"]}</td>";
        $output .= "<td><a href=\"view_blog.php?user_id=";
        $output .= urlencode($id);
        $output .= "&blog_id=";
        $output .= urlencode($blogs["id"]);
        $output .= "\">view & edit</a></td>";
        $output .= "</tr>";
    }
    $output .= "</table>";
    return $output;
}