Fixes PHP 8 compatibility issues.

[yuliu]

1. The issue for tracking: Fix PHP 8 compatibility issues since version 1.8.31 #4593.
2. The message of each commit explains what it fixes (the PHP 8 compatibility issue).
3. The PR includes fixes for issues reported in undefined variable $usersbrowsing in eval()'d code (92) in ./showthread.php(1617). #4602.
4. The PR includes fixes for some issues reported in Mark forum read doesn't work with php 8.0 #4530 (comment) . This one may be closed when the PR is merged, since other issues reported in it can't be reproduced.
5. The PR doesn't fix all remaining PHP 8 compatibility issues. That means there are still more.
6. Some more commits will be pushed later, before marking the PR as ready.

[yuliu]

In commit 6b2fa22

• Move post(s):
  • Undefined variable $return_url in eval()'d code (L27) in moderation.php (L2669).

Note: not sure if the variable $return_url used in template moderation_inline_moveposts is truly needed.

[yuliu]

Remarks in commit 64e8476

• $pm['saveasdraft'] and $pm['options']['XXX'] are added following how a pm is prepared in send_pm():
  

  mybb/inc/functions.php

  Lines 9079 to 9085 in c3c474a

  	$pm['options'] = array(
  	"disablesmilies" => 0,
  	"savecopy" => 0,
  	"readreceipt" => 0
  	);
  	$pm['saveasdraft'] = 0;

• $pm['saveasdraft'] = 0 is optional because the default for this option is 0.
• $pm['options']['signature'] is set to 0, given that the pms are to inform moderators/admins of a report.

[Eldenroot]

Will be merged into 1.8.33?

[yuliu]

Remarks for commit 128f8ea

• This is only a workaround for eliminating PHP warnings caused by the real issue reported in PrivateMessages formerly sent by any now deleted users will be recognized as sent by "MyBB Engine" #4630.

[yuliu]

Remarks for commit b153eb7

• The fixed typo here (canonlyviewownthread -> canonlyviewownthreads) doesn't fully resolve the PHP warning issue:

  Warning [2] Undefined array key "canonlyviewownthreads" - Line: 1228 - File: inc\datahandlers\post.php PHP 8.1.13
  

• The real issue behind this typo fix is about getting forum permissions:

  • forum_permissions() which calls
  • fetch_forum_permissions() that may return a set of group permissions where relevant permissions are missing --- those only exist in forum permissions (stored in mybb_forumpermissions) but not usergroup permissions (in mybb_usergroups), e.g., canonlyviewownthreads, canonlyreplyownthreads, etc.

[yuliu]

Since the code base is already in v1.8.33, while the PR is based on v1.8.32, it'll cost much more time to pinpoint recent reported issues.

More PHP 8 compatibility issues will be addressed in other PRs, and this one is marked as ready for review.

[yuliu]

More issues relating to the video mycode parsing have been reported in https://community.mybb.com/thread-237617.html . I'll push some commits that'll cover these issues later, to this PR.

[kgraefe]

Not sure if that's the right place, but I found some more in the admin panel of MyBB 1.8.33 that are not yet fixed, as far as I can tell from scanning through the PR:

This only happens when a view is selected that does not match any user.

Edit: You probably guessed it, but FTR: the error happens on PHP 8.0, 8.1 and 8.2. It does not occur on PHP 7.4.

[yuliu]

Remarks for commit d0af363

• The commit should have fixed all issues related to the parser reported in https://community.mybb.com/thread-237617.html .

• The following line was removed as the variable $title isn't used in the video_metacafe_embed template or anywhere else in the parser class. The removal may affect plugins that rely on the variable.

  mybb/inc/class_parser.php

  Line 1531 in c3c474a

  $title = htmlspecialchars_uni($path[3]);

• Currently, the parser can't correctly deal with URLs with any number of continuous / in its path part. [REF]