Source

File: wp-includes/class-wp-customize-manager.php

public function set_post_value( $setting_id, $value ) {
		$this->unsanitized_post_values(); // Populate _post_values from $_POST['customized'].
		$this->_post_values[ $setting_id ] = $value;

		/**
		 * Announce when a specific setting's unsanitized post value has been set.
		 *
		 * Fires when the WP_Customize_Manager::set_post_value() method is called.
		 *
		 * The dynamic portion of the hook name, `$setting_id`, refers to the setting ID.
		 *
		 * @since 4.4.0
		 *
		 * @param mixed                $value Unsanitized setting post value.
		 * @param WP_Customize_Manager $this  WP_Customize_Manager instance.
		 */
		do_action( "customize_post_value_set_{$setting_id}", $value, $this );

		/**
		 * Announce when any setting's unsanitized post value has been set.
		 *
		 * Fires when the WP_Customize_Manager::set_post_value() method is called.
		 *
		 * This is useful for `WP_Customize_Setting` instances to watch
		 * in order to update a cached previewed value.
		 *
		 * @since 4.4.0
		 *
		 * @param string               $setting_id Setting ID.
		 * @param mixed                $value      Unsanitized setting post value.
		 * @param WP_Customize_Manager $this       WP_Customize_Manager instance.
		 */
		do_action( 'customize_post_value_set', $setting_id, $value, $this );
	}