src/Debug/Output/Base.php
protected function dumpString($val)
    {
        if (\is_numeric($val)) {
            $date = $this->checkTimestamp($val);
            return $date
                ? $val.' ('.$date.')'
                : $val;
        } else {
            return $this->debug->utf8->dump($val);
        }
    }
protected function dumpString($val)
    {
        if (\is_numeric($val)) {
            $date = $this->checkTimestamp($val);
            return $date
                ? $val.' ('.$date.')'
                : $val;
        } else {
            return $this->debug->utf8->dump($val);
        }
    }
Dump string

@param string $val string value

@return string