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Edit File: class-wp-customize-background-image-setting.php
<?php /** * Customize API: WP_Customize_Background_Image_Setting class * * @package WordPress * @subpackage Customize * @since 4.4.0 */ /** * Customizer Background Image Setting class. * * @since 3.4.0 * * @see WP_Customize_Setting */ final class WP_Customize_Background_Image_Setting extends WP_Customize_Setting { /** * Unique string identifier for the setting. * * @since 3.4.0 * @var string */ public $id = 'background_image_thumb'; /** * @since 3.4.0 * * @param mixed $value The value to update. Not used. */ public function update( $value ) { remove_theme_mod( 'background_image_thumb' ); } }