private static function getPlaceholders(string $content): array
    {
        $result = [];
        $matchCount = preg_match_all(static::getPlaceholderPattern(), $content, $result);

        if (false !== $matchCount && 0 < $matchCount) {
            foreach ($result as $index => $placeholders) {
                $result[$index] = array_unique($placeholders);
            }
        }

        return $result;
    }