* Customizer bootstrap instance.

	 *

	 * @since 3.4.0

	 * Unique string identifier for the setting.

	 *

	 * @since 3.4.0

	 * Type of customize settings.

	 *

	 * @since 3.4.0

	 * @since 3.4.0

	 * @var string|array

	 * @since 3.4.0

	 * @var string

	 */

	public $theme_supports = '';

	/**

	 * The default value for the setting.

	 *

	 * @since 3.4.0

	 * @var string

	 */

	public $default = '';

	/**

	 * Options for rendering the live preview of changes in Theme Customizer.

	 *

	 * Set this value to 'postMessage' to enable a custom Javascript handler to render changes to this setting

	 * as opposed to reloading the whole page.

	 *

	 * @link https://developer.wordpress.org/themes/customize-api

	 *

	 * @since 3.4.0

	public $transport = 'refresh';

	/**

	 * Server-side validation callback for the setting's value.

	 *

	 * @since 4.6.0

	 * @var callable

	 */

	public $validate_callback = '';

	 * Callback to filter a Customize setting value in un-slashed form.

	 * @since 3.4.0

	 * @var callable

	public $sanitize_callback = '';

	/**

	 * Callback to convert a Customize PHP setting value to a value that is JSON serializable.

	 *

	 * @since 3.4.0

	 * @var string

	 */

	/**

	 * ID Data.

	 *

	 * @since 3.4.0

	 * @var array

	 */

	 * Whether or not preview() was called.

	 *

	 * @since 4.4.0

	 * @var bool

	 */

	protected $is_previewed = false;

	/**

	 * Cache of multidimensional values to improve performance.

	 *

	 * @since 4.4.0

	 * @static

	 * @var array

	 */

	protected static $aggregated_multidimensionals = array();

	/**

	 * Whether the multidimensional setting is aggregated.

	 *

	 * @since 4.4.0

	 * @var bool

	 */

	protected $is_multidimensional_aggregated = false;

	/**

			if ( isset( $args[ $key ] ) ) {

			}

		$this->id_data['keys'] = preg_split( '/\[/', str_replace( ']', '', $this->id ) );

		$this->id_data['base'] = array_shift( $this->id_data['keys'] );

		if ( ! empty( $this->id_data[ 'keys' ] ) ) {

			$this->id .= '[' . implode( '][', $this->id_data['keys'] ) . ']';

		}

		if ( $this->validate_callback ) {

			add_filter( "customize_validate_{$this->id}", $this->validate_callback, 10, 3 );

		}

		if ( $this->sanitize_callback ) {

			add_filter( "customize_sanitize_{$this->id}", $this->sanitize_callback, 10, 2 );

		}

		if ( $this->sanitize_js_callback ) {

			add_filter( "customize_sanitize_js_{$this->id}", $this->sanitize_js_callback, 10, 2 );

		}

		if ( 'option' === $this->type || 'theme_mod' === $this->type ) {

			// Other setting types can opt-in to aggregate multidimensional explicitly.

			$this->aggregate_multidimensional();

			// Allow option settings to indicate whether they should be autoloaded.

			if ( 'option' === $this->type && isset( $args['autoload'] ) ) {

				self::$aggregated_multidimensionals[ $this->type ][ $this->id_data['base'] ]['autoload'] = $args['autoload'];

			}

		}

	}

	/**

	 * Get parsed ID data for multidimensional setting.

	 *

	 * @since 4.4.0

	 *

	 * @return array {

	 *     ID data for multidimensional setting.

	 *

	 *     @type string $base ID base

	 *     @type array  $keys Keys for multidimensional array.

	 * }

	 */

	final public function id_data() {

		return $this->id_data;

	 * Set up the setting for aggregated multidimensional values.

	 *

	 * When a multidimensional setting gets aggregated, all of its preview and update

	 * calls get combined into one call, greatly improving performance.

	 *

	 * @since 4.4.0

	 */

	protected function aggregate_multidimensional() {

		$id_base = $this->id_data['base'];

		if ( ! isset( self::$aggregated_multidimensionals[ $this->type ] ) ) {

			self::$aggregated_multidimensionals[ $this->type ] = array();

		}

		if ( ! isset( self::$aggregated_multidimensionals[ $this->type ][ $id_base ] ) ) {

			self::$aggregated_multidimensionals[ $this->type ][ $id_base ] = array(

				'previewed_instances'       => array(), // Calling preview() will add the $setting to the array.

				'preview_applied_instances' => array(), // Flags for which settings have had their values applied.

				'root_value'                => $this->get_root_value( array() ), // Root value for initial state, manipulated by preview and update calls.

			);

		}

		if ( ! empty( $this->id_data['keys'] ) ) {

			// Note the preview-applied flag is cleared at priority 9 to ensure it is cleared before a deferred-preview runs.

			add_action( "customize_post_value_set_{$this->id}", array( $this, '_clear_aggregated_multidimensional_preview_applied_flag' ), 9 );

			$this->is_multidimensional_aggregated = true;

		}

	}

	/**

	 * Reset `$aggregated_multidimensionals` static variable.

	 *

	 * This is intended only for use by unit tests.

	 *

	 * @since 4.5.0

	 * @ignore

	 */

	static public function reset_aggregated_multidimensionals() {

		self::$aggregated_multidimensionals = array();

	}

	/**

	 * The ID for the current site when the preview() method was called.

	 * Return true if the current site is not the same as the previewed site.

	 * @return bool If preview() has been called.

			return false;

	 * Add filters to supply the setting's value when accessed.

	 *

	 * If the setting already has a pre-existing value and there is no incoming

	 * post value for the setting, then this method will short-circuit since

	 * there is no change to preview.

	 * @since 4.4.0 Added boolean return value.

	 *

	 * @return bool False when preview short-circuits due no change needing to be previewed.

		// Prevent re-previewing an already-previewed setting.

		if ( $this->is_previewed ) {

			return true;

		}

		$id_base = $this->id_data['base'];

		$is_multidimensional = ! empty( $this->id_data['keys'] );

		$multidimensional_filter = array( $this, '_multidimensional_preview_filter' );

		/*

		 * Check if the setting has a pre-existing value (an isset check),

		 * and if doesn't have any incoming post value. If both checks are true,

		 * then the preview short-circuits because there is nothing that needs

		 * to be previewed.

		 */

		$undefined = new stdClass();

		$needs_preview = ( $undefined !== $this->post_value( $undefined ) );

		$value = null;

		// Since no post value was defined, check if we have an initial value set.

		if ( ! $needs_preview ) {

			if ( $this->is_multidimensional_aggregated ) {

				$root = self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['root_value'];

				$value = $this->multidimensional_get( $root, $this->id_data['keys'], $undefined );

			} else {

				$default = $this->default;

				$this->default = $undefined; // Temporarily set default to undefined so we can detect if existing value is set.

				$value = $this->value();

				$this->default = $default;

			}

			$needs_preview = ( $undefined === $value ); // Because the default needs to be supplied.

		}

		// If the setting does not need previewing now, defer to when it has a value to preview.

		if ( ! $needs_preview ) {

			if ( ! has_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) ) ) {

				add_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) );

			}

			return false;

		}

		switch ( $this->type ) {

				if ( ! $is_multidimensional ) {

					add_filter( "theme_mod_{$id_base}", array( $this, '_preview_filter' ) );

				} else {

					if ( empty( self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'] ) ) {

						// Only add this filter once for this ID base.

						add_filter( "theme_mod_{$id_base}", $multidimensional_filter );

					}

					self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'][ $this->id ] = $this;

				}

				if ( ! $is_multidimensional ) {

					add_filter( "pre_option_{$id_base}", array( $this, '_preview_filter' ) );

				} else {

					if ( empty( self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'] ) ) {

						// Only add these filters once for this ID base.

						add_filter( "option_{$id_base}", $multidimensional_filter );

						add_filter( "default_option_{$id_base}", $multidimensional_filter );

					}

					self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'][ $this->id ] = $this;

				 * Fires when the WP_Customize_Setting::preview() method is called for settings

				 * @param WP_Customize_Setting $this WP_Customize_Setting instance.

				 * Fires when the WP_Customize_Setting::preview() method is called for settings

				 * @param WP_Customize_Setting $this WP_Customize_Setting instance.

		$this->is_previewed = true;

		return true;

	 * Clear out the previewed-applied flag for a multidimensional-aggregated value whenever its post value is updated.

	 *

	 * This ensures that the new value will get sanitized and used the next time

	 * that `WP_Customize_Setting::_multidimensional_preview_filter()`

	 * is called for this setting.

	 *

	 * @since 4.4.0

	 *

	 * @see WP_Customize_Manager::set_post_value()

	 * @see WP_Customize_Setting::_multidimensional_preview_filter()

	 */