frist create a custom widget class that extend the default wordpress widget class this code is from the official wordpress code reference
class My_Widget extends WP_Widget {
/**
* Sets up the widgets name etc
*/
public function __construct() {
$widget_ops = array(
'classname' => 'my_widget',
'description' => 'My Widget is awesome',
);
parent::__construct( 'my_widget', 'My Widget', $widget_ops );
}
/**
* Outputs the content of the widget
*
* @param array $args
* @param array $instance
*/
public function widget( $args, $instance ) {
// outputs the content of the widget
}
/**
* Outputs the options form on admin
*
* @param array $instance The widget options
*/
public function form( $instance ) {
// outputs the options form on admin
}
/**
* Processing widget options on save
*
* @param array $new_instance The new options
* @param array $old_instance The previous options
*
* @return array
*/
public function update( $new_instance, $old_instance ) {
// processes widget options to be saved
}
}
I this this code is very well explain and I don't need to comment it
this is a litle foobar widget example
/**
* Adds Foo_Widget widget.
*/
class Foo_Widget extends WP_Widget {
/**
* Register widget with WordPress.
*/
function __construct() {
parent::__construct(
'foo_widget', // Base ID
esc_html__( 'Widget Title', 'text_domain' ), // Name
array( 'description' => esc_html__( 'A Foo Widget', 'text_domain' ), ) // Args
);
}
/**
* 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 ) {
echo $args['before_widget'];
if ( ! empty( $instance['title'] ) ) {
echo $args['before_title'] . apply_filters( 'widget_title', $instance['title'] ) . $args['after_title'];
}
echo esc_html__( 'Hello, World!', 'text_domain' );
echo $args['after_widget'];
}
/**
* Back-end widget form.
*
* @see WP_Widget::form()
*
* @param array $instance Previously saved values from database.
*/
public function form( $instance ) {
$title = ! empty( $instance['title'] ) ? $instance['title'] : esc_html__( 'New title', 'text_domain' );
?>
<p>
<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php esc_attr_e( 'Title:', 'text_domain' ); ?></label>
<input class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>">
</p>
<?php
}
/**
* 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 = array();
$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? sanitize_text_field( $new_instance['title'] ) : '';
return $instance;
}
} // class Foo_Widget
register the widget in fuctions.php like this
// register Foo_Widget widget
function register_foo_widget() {
register_widget( 'Foo_Widget' );
}
add_action( 'widgets_init', 'register_foo_widget' );