function flagWords(string $text, array $badwords): string
{
    sort($badwords, SORT_STRING);
    $badword = reset($badwords);
    while ($badword) {
        $text = preg_replace(
            '/('. preg_quote($badword) .')/i',
            '<span style="color:red;">$1</span>',
            $text
        );
        $badword = next($badwords);
    }

    return $text;
}