src/Blocks/Inline/BlockStrongItalic.php
protected function convertUnderscores($lineContent)
    {
        return preg_replace_callback('/([\_]{3})(\S+)(.*)(\S+)([\_]{3})/U', function ($found) {
            return $this->getStartTag() . str_replace(static::TRIPLE_UNDERSCORES, '', $found[0]) . $this->getEndTag();
        }, $lineContent);
    }
protected function convertUnderscores($lineContent)
    {
        return preg_replace_callback('/([\_]{3})(\S+)(.*)(\S+)([\_]{3})/U', function ($found) {
            return $this->getStartTag() . str_replace(static::TRIPLE_UNDERSCORES, '', $found[0]) . $this->getEndTag();
        }, $lineContent);
    }
@param string $lineContent

@return string