Wordpress widget

wp-basic-widget.php

<?php
/**
 * Extend WP_Widget class,
 * 
 * Reference:
 * https://codex.wordpress.org/Widgets_API
 * https://codex.wordpress.org/Function_Reference/the_widget
 */

// Creating the widget 
class Tmx_widget extends WP_Widget {

    function __construct() {
        parent::__construct(
            // Base ID of your widget
            'tmx_widget', 

            // Widget name will appear in UI
            __('ThemeAxe Widget', 'tmx_widget_domain'), 

            // Widget description
            array( 'description' => __( 'Sample widget based on Tutorial', 'tmx_widget_domain' ), ) 
        );
    }

    // Creating widget front-end
    // This is where the action happens
    public function widget( $args, $instance ) {
        $title = apply_filters( 'widget_title', $instance['title'] );
        // before widget arguments are defined by themes
        echo $args['before_widget'];
        if ( ! empty( $title ) )
            echo $args['before_title'] . $title . $args['after_title'];

        // This is where you run the code and display the output
        echo __( 'Hello, World!', 'tmx_widget_domain' );

        // after widget arguments are defined by themes
        echo $args['after_widget'];
    }

    // Widget Backend 
    public function form( $instance ) {
        if ( isset( $instance[ 'title' ] ) ) {
            $title = $instance[ 'title' ];
        }
        else {
            $title = __( 'New title', 'tmx_widget_domain' );
        }
        // Widget admin form
        ?>
            <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 esc_attr( $title ); ?>" />
            </p>
            <?php 
    }

    // Updating widget replacing old instances with new
    public function update( $new_instance, $old_instance ) {
        $instance = array();
        $instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';
        return $instance;
    }
} // Class tmx_widget ends here

// Register and load the widget
function tmx_load_widget() {
	register_widget( 'Tmx_widget' );
}
add_action( 'widgets_init', 'tmx_load_widget' );