A PHP Error was encountered

Severity: Notice

Message: Trying to access array offset on value of type null

Filename: controllers/Join.php

Line Number: 60

Backtrace:

File: /data/user/htdocs/public/app/index/controllers/Join.php
Line: 60
Function: _error_handler

File: /data/user/htdocs/public/index.php
Line: 322
Function: require_once