WordPress: Image upload in a widget

gistfile1.php

<?php
/**
 * NGData Widget Icons
 *
 * @author Lisa Sabin-Wilson
 * @since 1.0
 */


class icon_text extends WP_Widget
{

  function icon_text() {
		$widget_ops = array(
			'classname' => 'icon-text group',
			'description' => __( 'Arbitrary text or HTML, with a simple icon near title.', 'ngdata' )
		);

		$control_ops = array( 'id_base' => 'icon-text', 'width' => 430 );

		$this->WP_Widget( 'icon-text', 'NGDATA Icon Text Widget', $widget_ops, $control_ops );

		wp_enqueue_style( 'thickbox' );
		wp_enqueue_script( 'thickbox' );
		//wp_enqueue_script( 'media-upload' );
		add_action( 'admin_print_footer_scripts', array( &$this, 'add_script_textimage' ), 999 );
	}

	function form( $instance ) {

		/* Impostazioni di default del widget */
		$defaults = array(
			'title' => '',
			'text' => '',
			'img_url' => '',
			'widget_url' => ''
		);

		$instance = wp_parse_args( (array) $instance, $defaults ); ?>

		<p>
			<label>
				<strong><?php _e( 'Title', 'ngdata' ) ?>:</strong><br />
				<input class="widefat" type="text" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" value="<?php echo $instance['title']; ?>" />
			</label>
		</p>

		<p>
			<label for="<?php echo $this->get_field_id('img_url'); ?>">Image</label><br />
			<input type="text" class="img" name="<?php echo $this->get_field_name('img_url'); ?>" id="<?php echo $this->get_field_id('img_url'); ?>" value="<?php echo $instance['img_url']; ?>" />
			<input type="button" class="select-img" value="Select Image" />
		</p>

		<p>
			<label>
				<textarea class="widefat" id="<?php echo $this->get_field_id( 'text' ); ?>" name="<?php echo $this->get_field_name( 'text' ); ?>" cols="20" rows="5"><?php echo $instance['text']; ?></textarea>
			</label>
		</p>
		<p>
			<label>
				<strong><?php _e( 'URL', 'ngdata' ) ?>:</strong><br />
				<input class="widefat" type="text" id="<?php echo $this->get_field_id( 'widget_url' ); ?>" name="<?php echo $this->get_field_name( 'widget_url' ); ?>" value="<?php echo $instance['widget_url']; ?>" />
			</label>
		</p>
		<?php
	}

	function widget( $args, $instance ) {
		extract( $args );

		$title = apply_filters( 'widget_title', $instance['title'] );
		$widget_url = $instance['widget_url'];
		$img_url = $instance['img_url'];
		echo $before_widget;
?>

		<a href="<?php echo $widget_url ?>">
			<img src="<?php echo $img_url ?>" alt="" />

			<h3><?php echo $title; ?></h3>
			<p><?php echo do_shortcode( $instance['text'] ) ?></p>
		</a>

		<?php echo $after_widget;
	}

	function update( $new_instance, $old_instance ) {
		$instance = $old_instance;

		$instance['title'] = strip_tags( $new_instance['title'] );

		$instance['img_url'] = $new_instance['img_url'];

		$instance['text'] = $new_instance['text'];

		$instance['widget_url'] = $new_instance['widget_url'];

		return $instance;
	}

	function add_script_textimage() {
?>
<script type="text/javascript">
	var image_field;
	jQuery(function($){
		$(document).on('click', 'input.select-img', function(evt){
			image_field = $(this).siblings('.img');
			tb_show('', 'media-upload.php?type=image&amp;TB_iframe=true');
			return false;
		});
		window.send_to_editor = function(html) {
			image_field.val($(html).attr('src'));
			tb_remove();
		}
	});
</script>
<?php
	}


}

?>