Steps to reproduce the issue

One of our users upgraded the Joomla Software. I'm not sure of the exact upgrade that they did. Now, no one can login to Joomla to make changes. Once I try to login, I get this error:
Parse error: syntax error, unexpected '$this' (T_VARIABLE) in /home3/njcouns/public_html/administrator/components/com_civicrm/civicrm/CRM/Core/DAO.php on line 1123

I'm assuming that I need to revert back to a version before any changes were made. How do I fix this issue?

Expected result

Actual result

System information (as much as possible)

Additional comments