<form method="POST">
    <h3>Editing: CarouselSliderWidget.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

namespace CarouselSlider\Widget;

use CarouselSlider\Frontend\Frontend;
use CarouselSlider\Helper;
use WP_Widget;

defined( 'ABSPATH' ) || exit;

/**
 * CarouselSliderWidget class
 */
class CarouselSliderWidget extends WP_Widget {

	/**
	 * The instance of the class
	 *
	 * @var self
	 */
	protected static $instance;

	/**
	 * Ensures only one instance of the class is loaded or can be loaded.
	 *
	 * @return self
	 */
	public static function init() {
		if ( is_null( self::$instance ) ) {
			self::$instance = new self();

			add_action( 'widgets_init', [ self::$instance, 'register' ] );
		}

		return self::$instance;
	}

	/**
	 * Register current class as widget
	 */
	public static function register() {
		register_widget( __CLASS__ );
	}

	/**
	 * Get the list of carousel sliders
	 *
	 * @return array
	 */
	private static function carousels_list(): array {
		$posts = Helper::get_sliders();

		$items = [];
		foreach ( $posts as $post ) {
			$items[] = [
				'id'    =&gt; $post-&gt;ID,
				'title' =&gt; $post-&gt;post_title,
			];
		}

		return $items;
	}

	/**
	 * Sets up the widgets name etc
	 */
	public function __construct() {
		$widget_ops = array(
			'classname'   =&gt; 'widget_carousel_slider',
			'description' =&gt; __(
				'The easiest way to create image, video, post and WooCommerce product carousel.',
				'carousel-slider'
			),
		);
		parent::__construct( 'widget_carousel_slider', __( 'Carousel Slider', 'carousel-slider' ), $widget_ops );
	}

	/**
	 * Outputs the content of the widget
	 *
	 * @param  array $args  Display arguments including 'before_title', 'after_title',
	 *                       'before_widget', and 'after_widget'.
	 * @param  array $instance  The settings for the particular instance of the widget.
	 */
	public function widget( $args, $instance ) {
		$title       = isset( $instance['title'] ) ? esc_html( $instance['title'] ) : null;
		$carousel_id = isset( $instance['carousel_id'] ) ? absint( $instance['carousel_id'] ) : 0;

		if ( ! $carousel_id ) {
			return;
		}

		$html = $args['before_widget'];

		if ( ! empty( $title ) ) {
			$html .= $args['before_title'] . $title . $args['after_title'];
		}

		$html .= Frontend::init()-&gt;carousel_slide( [ 'id' =&gt; $carousel_id ] );
		$html .= $args['after_widget'];

		Helper::print_unescaped_internal_string( $html );
	}

	/**
	 * Outputs the settings update form.
	 *
	 * @param  array $instance  Current settings.
	 *
	 * @return void
	 */
	public function form( $instance ) {
		$carousels   = static::carousels_list();
		$carousel_id = ! empty( $instance['carousel_id'] ) ? absint( $instance['carousel_id'] ) : null;
		$title       = ! empty( $instance['title'] ) ? esc_attr( $instance['title'] ) : '';
		$html        = '';
		if ( count( $carousels ) &gt; 0 ) {
			$html .= sprintf(
				'&lt;p&gt;&lt;label for=&quot;%1$s&quot;&gt;%2$s&lt;/label&gt;',
				$this-&gt;get_field_id( 'title' ),
				__( 'Title (optional):', 'carousel-slider' )
			);
			$html .= sprintf(
				'&lt;input type=&quot;text&quot; class=&quot;widefat&quot; id=&quot;%1$s&quot; name=&quot;%2$s&quot; value=&quot;%3$s&quot; /&gt;&lt;/p&gt;',
				$this-&gt;get_field_id( 'title' ),
				$this-&gt;get_field_name( 'title' ),
				$title
			);

			$html .= sprintf( '&lt;p&gt;&lt;label&gt;%s&lt;/label&gt;', __( 'Choose Slide', 'carousel-slider' ) );
			$html .= sprintf( '&lt;select class=&quot;widefat&quot; name=&quot;%s&quot;&gt;', $this-&gt;get_field_name( 'carousel_id' ) );
			foreach ( $carousels as $carousel ) {
				$selected = $carousel['id'] === $carousel_id ? 'selected=&quot;selected&quot;' : '';
				$html    .= sprintf(
					'&lt;option value=&quot;%1$d&quot; %3$s&gt;%2$s&lt;/option&gt;',
					absint( $carousel['id'] ),
					esc_html( $carousel['title'] ),
					$selected
				);
			}
			$html .= '&lt;/select&gt;&lt;/p&gt;';

		} else {
			$html .= sprintf(
				'&lt;p&gt;%1$s &lt;a href=&quot;' . admin_url( 'post-new.php?post_type=carousels' ) . '&quot;&gt;%3$s&lt;/a&gt; %2$s&lt;/p&gt;',
				__( 'You did not add any carousel slider yet.', 'carousel-slider' ),
				__( 'to create a new carousel slider now.', 'carousel-slider' ),
				__( 'click here', 'carousel-slider' )
			);
		}

		echo $html; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
	}

	/**
	 * 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 ) {
		$old_instance['title']       = sanitize_text_field( $new_instance['title'] );
		$old_instance['carousel_id'] = absint( $new_instance['carousel_id'] );

		return $old_instance;
	}
}
</textarea><br>
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