PHP Parse error for folder path in Advanced mode

[mattmattox]

Error message:

[Sun Jun 20 06:52:00.213229 2021] [php7:error] [pid 35] [client 1.2.3.4:46738] PHP Parse error:  syntax error, unexpected '.' in /var/www/src/include/plugins/archiver/class.ArchiverPlugin.php on line 205, referer: https://example.com

Workaround:

$folder = $path . '/' . @Format::slugify ($dept) . '/' . @Format::slugify ($user) . '/' . @Format::slugify ("{$ticket->getSubject ()}_{$ticket->getNumber ()}");