public function reverse_left_and_right_background($value) {
		$values = $this->dissolve_short_bg($value);
		if (isset($values['background-position']) and $values['background-position']) {
			$v = $this->reverse_left_and_right_background_position($values['background-position']);
			if ($v !== $values['background-position']) {
				if ($value == $values['background-position']) {
					return $v;
				}
				else {
					$values['background-position'] = $v;
					$x = $this->merge_bg($values);
					if (isset($x['background'])) {
						return $x['background'];
					}
				}
			}
		}
		return $value;
	}