[Plugin: Testimonial] How To Manipulate Database From Admin Panel

Hello, I’m new to develop WordPress plugins. At this time, I’d try to build my own plugin which can be handle testimonials from front-end user. At the current, I have this 2 files of code and it did work to display form in the front-end web page.

‘ryadi-testimonial.php’

/**
 * Plugin Name: Ryadi Testimonial
 */

if(!isset($_SESSION)) session_start();
if ('ryadi-testimonial.php' == basename($_SERVER['SCRIPT_FILENAME']))
	die ('Please do not access this file directly. Thanks!');

function ryadi_testimonial_activate()
{
    global $wpdb;
    $tablename = $wpdb->prefix.'ryadi_testimonial';
    $charset_collate = '';
    if ( version_compare(mysql_get_server_info(), '4.1.0', '>=') )
    {
        if ( ! empty($wpdb->charset) )
                $charset_collate = " DEFAULT CHARACTER SET $wpdb->charset";
        if ( ! empty($wpdb->collate) )
                $charset_collate .= " COLLATE $wpdb->collate";
    }
    $sql = "CREATE TABLE IF NOT EXISTS <code>$tablename</code>
    (
       <code>rt_id</code> int(4) UNSIGNED NOT NULL AUTO_INCREMENT,
       <code>rt_date</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
       <code>rt_approved</code> int(1) UNSIGNED NOT NULL,
       <code>rt_name</code> char(100) NOT NULL,
       <code>rt_email</code> char(100) NOT NULL,
       <code>rt_pic_url</code> char(150) NOT NULL,
       <code>rt_testimonial</code> text NOT NULL,
       PRIMARY KEY (<code>rt_id</code>)
    )$charset_collate;";
    require_once ( ABSPATH . 'wp-admin/includes/upgrade.php');
    dbDelta($sql);
}
register_activation_hook( __FILE__, 'ryadi_testimonial_activate' );

function ryadi_testimonial_plugin_setup()
{
	require_once( dirname(__FILE__).'/widgets/ryadi-input-testimonial-widget.php' );
	load_plugin_textdomain('testimonial-basics', false, 'testimonial-basics/languages');
}
add_action( 'plugins_loaded','ryadi_testimonial_plugin_setup');

‘widgets/ryadi-input-testimonial-widget’

/*
Plugin Name: Ryadi Testimonial Input Widget
*/

if(!isset($_SESSION)) session_start();

function ryadi_input_testimonial_widget()
{
    register_widget ( 'ryadi_input_testimonial_widget' );
}
add_action ( 'widgets_init','ryadi_input_testimonial_widget' );

class ryadi_input_testimonial_widget extends WP_Widget
{
    function ryadi_input_testimonial_widget()
    {
        $widget_ops = array
        (
            'classname' => 'ryadi_input_widget_class',
            'description' => __('This widget will allow a user to input a testimonial.','ryadi-testimonial')
	);
        $this->WP_Widget( 'ryadi_input_testimonial_widget', __('Testimonial Input Widget','ryadi-testimonial'), $widget_ops );
    }

    function form($instance)
    {
        if ($instance)
        {
            $title = esc_attr($instance['title']);
            $text = esc_attr($instance['text']);
            $textarea = esc_textarea($instance['textarea']);
        }
        else
        {
            $title = '';
            $text = '';
            $textarea = '';
        }

        ?>
        <p>
        <label for="<?=$this->get_field_id('title'); ?>"><?php _e('Widget Title', 'ryadi-testimonial'); ?></label>
        <input class="widefat" id="<?=$this->get_field_id('title'); ?>" name="<?=$this->get_field_name('title'); ?>" type="text" value="<?=$title; ?>" />
        </p>

        <?php
    }

    function update($new_instance, $old_instance)
    {
        $instance = $old_instance;
        $instance['title'] = strip_tags($new_instance['title']);
        $instance['text'] = strip_tags($new_instance['text']);
        $instance['textarea'] = strip_tags($new_instance['textarea']);
        return $instance;
    }

    function widget($args, $instance)
    {
        extract( $args );
        $title = apply_filters('widget_title', $instance['title']);
        if (isset($_POST['rytitle']))
        {
            $rytitle = trim($_POST['rytitle']);
            $ryname = trim($_POST['ryname']);
            $ryemail = trim($_POST['ryemail']);
            $rytestimonial = trim($_POST['rytestimonial']);
            $ryerror = '';
            if ($rytitle == '' || $ryname == '' || $ryemail == '' || $rytestimonial == '')
            {
                $ryerror = 'Please fill all required fields';
            }
            else
            {
                //Do something
            }
        }
        else
        {
            $rytitle = '';
            $ryname = '';
            $ryemail = '';
            $rytestimonial = '';
        }
        echo $before_widget;
        ?>
        <div class="widget-text wp_widget_plugin_box">
            <?=( $title ) ? $before_title . $title . $after_title : 'Testimonials'?>
            <form method="post">
                <label>Title*</label><input name='rytitle' value="<?=$rytitle?>" /><br />
                <label>Name*</label><input name='ryname' value="<?=$ryname?>" /><br />
                <label>Email*</label><input name='ryemail' value="<?=$ryemail?>" /><br />
                <label>Testimonial*</label><input name='rytestimonial' value="<?=$rytestimonial?>" /><br />
                <?php if ($ryerror != '') : ?><label class="error-message"><?=$ryerror?></label><?php endif; ?><br />
                <input type="submit" name="rysubmit" value="SUBMIT" />
            </form>
        </div>
        <?php
        echo $after_widget;
    }

}

I don’t have any idea, how to create panel so I can manipulate (add, edit, delete) data entry from admin panel? It doesn’t matter for the security, I will learn it in the next level. Any link or help, I would be appreciate it. 🙂

Anyway, sorry for my english.