class-wp-customize-manager.php on line 2307

/*
* Get list of IDs for settings that have values different from what is currently
* saved in the changeset. By skipping any values that are already the same, the
* subset of changed settings can be passed into validate_setting_values to prevent
* an underprivileged modifying a single setting for which they have the capability
* from being blocked from saving. This also prevents a user from touching of the
* previous saved settings and overriding the associated user_id if they made no change.
*/
	$changed_setting_ids = array();
	foreach ( $post_values as $setting_id => $setting_value ) {
		$setting = $this->get_setting( $setting_id );

		if ( $setting && 'theme_mod' === $setting->type ) {
			$prefixed_setting_id = $this->get_stylesheet() . '::' . $setting->id;
		} else {
			$prefixed_setting_id = $setting_id;
		}

		$is_value_changed = (
			! isset( $existing_changeset_data[ $prefixed_setting_id ] )
			||
			! array_key_exists( 'value', $existing_changeset_data[ $prefixed_setting_id ] )
			||
			$existing_changeset_data[ $prefixed_setting_id ]['value'] !== $setting_value
		);
		if ( $is_value_changed ) {
			$changed_setting_ids[] = $setting_id;
		}
	}