Bug loading

[GMateus]

By changing the forum styles in version 3.1.12 which was the version reported in the styles used gave these errors in some posts.
Does anyone know what it might be?

[phpBB Debug] PHP Warning: in file [ROOT]/includes/bbcode.php on line 113: preg_replace(): Compilation failed: unrecognized character after (?< at offset 60
[phpBB Debug] PHP Warning: in file [ROOT]/includes/functions.php on line 5348: Cannot modify header information - headers already sent by (output started at [ROOT]/includes/functions.php:3937)

[Kailey]

Please fill out the Support Request Template and post it back here to enable us to assist you better.

[GMateus]

"Alpha and Beta versions are not supported. Please perform a fresh install using the latest version and then see if your problem persists."
Looks too simple...

[Kailey]

I would recommend going to 3.2 anyway.

Notes:

• Your server must be running at least PHP 5.4.7 or higher.
• phpBB 3.2 is not completely backwards compatible with 3.1 and custom edits may no longer work. The easiest upgrade method is to remove all existing files prior to upgrading and re-applying custom changes after verifying their correctness.
  
  To upgrade, perform the following steps:

1. Make a back-up of the original files and database
2. Deactivate all styles except for prosilver
3. Deactivate any extensions which are not compatible with phpBB 3.2. Check with the extension author to find out if an extension is compatible or not.
4. Ensure that the activated spambot countermeasure is one of the standard phpBB plugins (Simple image, GD image, GD 3D image, Q&A, reCaptacha).
5. Set British English as the only language pack and delete all other language pack directories from your server
6. Delete all of your phpBB 3.1.x files EXCEPT for the following:
   • The config.php file
   • The /ext/ directory
   • The /images/ directory
   • The /files/ directory
   • The /store/ directory
7. Upload the contents of the phpBB3 directory from the uncompressed 3.2.x Full Package (EXCEPT for config.php) into your forum's directory (Note: you don't want to overwrite your original config.php file)
8. Browse to www.example.com/install/
9. Click the Update tab
10. Click the Update button
11. Select "Update database only" and click Submit
12. Wait for the progress bar to reach 100% and for a message indicating that the update has completed
13. Delete or rename the /install/ directory