PHP 8.0 compatibility issues

[yuliu]

This issue will track the merge system's PHP 8.0 compatibility problem. Any PR fixing any of them is welcome.

[yuliu]

Warning: Declaration of debugErrorHandler::error($type, $message, $file = NULL, $line = 0) should be compatible with errorHandler::error($type, $message, $file = NULL, $line = 0, $allow_output = true) in /merge/resources/class_error.php on line 34

Already reported in #273, other reports from the community forum: https://community.mybb.com/thread-234192-post-1372839.html#pid1372839

[yuliu]

create_function() was removed in 8.0 PHP version.

https://github.com/mybb/merge-system/blob/755ae596ce1dd894e2861a22345a55fb5da77533/resources/functions.php#L728-L739

https://github.com/mybb/merge-system/blob/755ae596ce1dd894e2861a22345a55fb5da77533/boards/vbulletin3/privatemessages.php#L64

https://github.com/mybb/merge-system/blob/755ae596ce1dd894e2861a22345a55fb5da77533/boards/vbulletin4/privatemessages.php#L64

https://github.com/mybb/merge-system/blob/755ae596ce1dd894e2861a22345a55fb5da77533/boards/vbulletin5/privatemessages.php#L64

[yuliu]

From #279 bbpress's delcaration get_group_id() isn't compatible with parent class's

BBPRESS_Converter->get_group_id(): https://github.com/mybb/merge-system/blob/d453ec2b922a088cfa41a81753c37b7f038ecb77/boards/bbpress.php#L100

Converter->get_group_id(): https://github.com/mybb/merge-system/blob/d453ec2b922a088cfa41a81753c37b7f038ecb77/resources/class_converter.php#L531

[DMiurge]

anyone going to tackle the PHP8 incompability? PHP8 has been around for some time now. Why isn't the merge system still not working?