PHP Upgrade to 8.1 Results in Empty Pages

I am using PHPList V3.6.13 and it works perfect with PHP 7.4.33. However, when I upgrade to PHP 8.1.23 I only receive empty pages (logon, subscribe, etc.) If I revert back to PHP 7.4.33, everything works perfect again. I looked at the source code in the browser and there is nothing there either. I am using Firefox 117.0.1. I appreciate any help I can get.


@jwill Try enabling php error reporting. On this line in file admin/init.php change 0 to -1


Then look at the html source of the blank page. Also look in the php error log file.

This error is displayed in the source with error_reporting set to -1:

Fatal error: Declaration of sidebar::helloworld() must be compatible with phplistPlugin::HelloWorld($params) in /home/customer/www/ on line 6

@jwill You appear to have a very old plugin installed. Delete the file admin/plugins/sidebar.php and also helloworld.php if that also exists.

Thank you, that solved the problem.