How to create widget post in sidebar

<?php
/*
Plugin Name: flippercode Widget Pack
Plugin URI: http://flippercode.com
Description: A plugin containing various widgets created in a Flippercode series on WordPress widgets
Version: 0.1
Author: flippercode
Author URI: http://flippercode.com
Text Domain: flippercode
License: GPLv2

*/


class FlipperText_Widget extends WP_Widget {

    public function __construct() {
    
        parent::__construct(
            'flippertext_widget',
            __( 'Flipper Text Widget', 'flippertextdomain' ),
            array(
                'classname'   => 'flippertext_widget',
                'description' => __( 'A basic text widget to demo the flipper series on creating your own widgets.', 'flippertextdomain' )
                )
        );
      
        load_plugin_textdomain( 'flippertextdomain', false, basename( dirname( __FILE__ ) ) . '/languages' );
      
    }

    /** 
     * Front-end display of widget.
     *
     * @see WP_Widget::widget()
     *
     * @param array $args     Widget arguments.
     * @param array $instance Saved values from database.
     */
 public function widget( $args, $instance ) {
        if ( ! isset( $args['widget_id'] ) ) {
            $args['widget_id'] = $this->id;
        }

        $title = ( ! empty( $instance['title'] ) ) ? $instance['title'] : __( 'Recent Posts' );

        /** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
        $title = apply_filters( 'widget_title', $title, $instance, $this->id_base );

        $number = ( ! empty( $instance['number'] ) ) ? absint( $instance['number'] ) : 2;
        if ( ! $number )
            $number = 5;
        $show_date = isset( $instance['show_date'] ) ? $instance['show_date'] : false;

        /**
         * Filter the arguments for the Recent Posts widget.
         *
         * @since 3.4.0
         *
         * @see WP_Query::get_posts()
         *
         * @param array $args An array of arguments used to retrieve the recent posts.
         */
        $r = new WP_Query( apply_filters( 'widget_posts_args', array(
            'posts_per_page'      => $number,
            'no_found_rows'       => true,
            'post_status'         => 'publish',
            'ignore_sticky_posts' => true
        ) ) );

        if ($r->have_posts()) :
        ?>
        <?php echo $args['before_widget']; ?>
        <?php if ( $title ) {
            echo $args['before_title'] . $title . $args['after_title'];
        } ?>
        <ul>
        <?php while ( $r->have_posts() ) : $r->the_post(); ?>
            <li>
                <a href="<?php the_permalink(); ?>"><?php get_the_title() ? the_title() : the_ID(); ?></a>
            <?php if ( $show_date ) : ?>
                <span class="post-date"><?php echo get_the_date(); ?></span>
            <?php endif; ?>
            </li>
        <?php endwhile; ?>
        </ul>
        <?php echo $args['after_widget']; ?>
        <?php
        // Reset the global $the_post as this query will have stomped on it
        wp_reset_postdata();

        endif;
    }

 
    /**
      * Sanitize widget form values as they are saved.
      *
      * @see WP_Widget::update()
      *
      * @param array $new_instance Values just sent to be saved.
      * @param array $old_instance Previously saved values from database.
      *
      * @return array Updated safe values to be saved.
      */
    public function update( $new_instance, $old_instance ) {       
        
        $instance = $old_instance;
        $instance['title'] = sanitize_text_field( $new_instance['title'] );
        $instance['number'] = (int) $new_instance['number'];
        $instance['show_date'] = isset( $new_instance['show_date'] ) ? (bool) $new_instance['show_date'] : false;
        return $instance;
        
    }
 
    /**
      * Back-end widget form.
      *
      * @see WP_Widget::form()
      *
      * @param array $instance Previously saved values from database.
      */
    public function form( $instance ) {   
    
        $title     = isset( $instance['title'] ) ? esc_attr( $instance['title'] ) : '';
        $number    = isset( $instance['number'] ) ? absint( $instance['number'] ) : 2;
        $show_date = isset( $instance['show_date'] ) ? (bool) $instance['show_date'] : false;
        ?>
        
        <p><label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
        <input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo $title; ?>" /></p>

        <p><label for="<?php echo $this->get_field_id( 'number' ); ?>"><?php _e( 'Number of posts to show:' ); ?></label>
        <input class="tiny-text" id="<?php echo $this->get_field_id( 'number' ); ?>" name="<?php echo $this->get_field_name( 'number' ); ?>" type="number" step="1" min="1" value="<?php echo $number; ?>" size="3" /></p>

        <p><input class="checkbox" type="checkbox"<?php checked( $show_date ); ?> id="<?php echo $this->get_field_id( 'show_date' ); ?>" name="<?php echo $this->get_field_name( 'show_date' ); ?>" />
        <label for="<?php echo $this->get_field_id( 'show_date' ); ?>"><?php _e( 'Display post date?' ); ?></label></p>
    
    <?php
    }
    
}

/* Register the widget */
add_action( 'widgets_init', function(){
     register_widget( 'flippertext_widget' );
});

How to create backend plugin in wordpress

<?php /*
Plugin Name: book management
Description: This plugin will add/edit/delete Funding Method.
Author: Brainz Technologies
Version: 1.0
*/
$siteurl = get_option('siteurl');
define('BOOKMETHD_FOLDER', dirname(plugin_basename(__FILE__)));
define('BOOKMETHD_URL', $siteurl.'/wp-content/plugins/' . BOOKMETHD_FOLDER);
define('BOOKMETHD_FILE_PATH', dirname(__FILE__));
define('BOOKMETHD_DIR_NAME', basename(BOOKMETHD_FILE_PATH));

// this is the table prefix
global $wpdb;
$bookmethd_table_prefix = $wpdb->prefix;
define('BOOKMETHD_TABLE_PREFIX', $bookmethd_table_prefix);

register_activation_hook(__FILE__,'bookmethd_install');
register_deactivation_hook(__FILE__ ,'bookmethd_uninstall');

//table will be created when plugin is activated.
function bookmethd_install()
{
    global $wpdb;
    $table     = BOOKMETHD_TABLE_PREFIX."book_methods";
    $structure = "CREATE TABLE $table (
                 id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,               
                 book_name VARCHAR(150) NOT NULL,
                 author VARCHAR(150) NOT NULL,
                 department VARCHAR(150) NOT NULL,
                price VARCHAR(150) NOT NULL,
                quantity VARCHAR(150) NOT NULL
                 );";
    $wpdb->query($structure);   
}

//table will be deleted when plugin is deactivated.
function bookmethd_uninstall()
{
    global $wpdb;
    $table     =  BOOKMETHD_TABLE_PREFIX."book_methods";
    $structure =  "DROP TABLE if exists $table";
    $wpdb->query($structure);
}

//show menu on left side
add_action('admin_menu','bookmethd_admin_menu');
function bookmethd_admin_menu(){
  add_menu_page('book Method','Manage book', 10, 'manage_book_method', 'wps_manage_book_method','21');
  add_submenu_page('manage_book_method','Add book ','Add new book',10,'addEdit_book_method','wps_addEdit_book_method');
}

function wps_manage_book_method(){
    include 'manage_book.php';
}


function wps_addEdit_book_method(){   
    $action  = $_GET['action'];
    if($action=='edit'){
        include 'addedit_book_method.php';
    }else{
        include 'add_book.php';       
    }
}

?>
<script type="text/javascript">
function deletebookName(id){ 
  if(confirm("Are you sure to delete?")){ 
   jQuery.ajax({
        url: "../wp-content/plugins/reg_form/delete_book_name.php",
        type: 'post',
        dataType: "html",
        data: { f_ID: id },
        success: function( data ) {
            window.location.href = "../wp-admin/admin.php?page=manage_book_method";
        }
    });
  }
}
</script>
<?php
function getdata( $atts )
{
  global $wpdb;
   $table = $wpdb->prefix."book_methods";
  if(!empty($atts['book_names_id']))  {
  echo "<pre>";
  print_r($atts);
 $book_names = $wpdb->get_results("SELECT * FROM $table where id='".($atts['book_names_id'])."'");
 }
 else
 {
 $book_names = $wpdb->get_results("SELECT * FROM $table");
 }
 $htm="";
 $htm.="<table border='0' cellpadding='2' cellspacing='2' width='70%' style='border:5px solid #cdcdcd;'>
 <tr><td><b>ID.No.</b></td>
 <td><b>Book name</b></td>
 <td><b>Author</b></td>
 <td><b>Department</b></td>
 <td><b>price</b></td>
 <td><b>Quantity</b></td>
  </tr>";
  if($book_names){
      $i=1;
     foreach($book_names as $book){
          $book_names_id=  $book->id;       
          $book_name   = $book->book_name;
           $author  = $book->author;
            $department     = $book->department;
             $price  = $book->price;
           $quantity  = $book->quantity;
  $htm.='<tr><td>'.$book_names_id.'</td>
  <td>'.$book_name.'</td>
  <td>'.$author.'</td>
  <td>'.$department.'</td>
  <td>'.$price.'</td>
  <td>'.$quantity.'</td>
  </tr>';
  }
  $htm.='</table>';
print $htm;
  }
  }
add_shortcode('arjun', 'getdata');


?>