Search your template (and overrides) for the use of the "count()" function. Then solve the errors like so:

www.joomlaworks.net/forum/k2-en/59481-error-message-after-upgrade-to-php8-0-fpm#178585

I got the following answer from the support team. Fingers crossed that SigPRO for J4 will arive this year.

Hi there Peter, I'm currently working on K2 for J4 (which is a huge task). Once that is done (hopefully around September), SIGPro is next in line for an upgrade. You can always use the free version which is J4 compatible and once SIGPro is also available for J4, you can seamlessly upgrade. Regards, JoomlaWorks Support Team

I got the following answer from the support team. Fingers crossed that SigPRO for J4 will arive this year.

Hi there Peter, I'm currently working on K2 for J4 (which is a huge task). Once that is done (hopefully around September), SIGPro is next in line for an upgrade. You can always use the free version which is J4 compatible and once SIGPro is also available for J4, you can seamlessly upgrade. Regards, JoomlaWorks Support Team

Hi Catherine,
my solution is now, all done at Joomla 3 before upgrade:
- Make a export-list of K2-items with attachments, 1 attachment in a row. I need the columns itemID and name of the attachment-file
- Install JA K2 Data Migration plugin and migrate all K2-items, categories and fields to Joomla article
- Install Advanced Custom Fields
- Create a Custom Field File-upload, you need the field-ID for the import-script
- Move the download-files from /media/k2/attachments to /media/acfupload
- Than I replaced in my K2-item-export-list the old item-ID to the new item-ID. (Excel, SVERWEIS) Attention: By importing the items they became a new
- With a little php-script I created a sql-file an than I imported the file with phpMyAdmin to __fields_values, backup before.
This way I imported more than 500 files in 170 items, and it worked.

If there is an easier way, please let me know.

Best regards,
Gabi

I upgraded to 4SEF. However, the generated URLs don't work as required, new menu items generated use the menu URLs. I have the K2 sh404sef plug-in configured to use the categories in the URL, but this doesn't work with 4SEF.

I have reverted back to sh404sef for now. Hopefully K2 for Joomla 4 will work with 4SEF correctly with a new K2 plugin.

For now, here: github.com/getk2/k2/commits/master

This info will be aggragated into a nice CHANGELOG page soon on getk2.org as well.

Sorry for this guys.

The issue is now resolved. Just re-install K2.

The version is still the same for the record as it's tied to the same day.

A new option will also be added in a few days to switch between full category paths or single category paths (the current default) in both item and category URLs.

Release snapshots are available here: getk2.org/downloads/

Since Oleksander messaged me already and provided his Custom SEF setup, Morten could you please do the same as well? Just grab a screenshot of your Custom SEF settings in K2's component settings and upload it here.

After upgrade K2 to version 2.11 March 23 I had 404 error on all articles
How to fix the error or at least download K2 to version 2.11 of an older version

I've actually gone ahead and updated the URL router. Version 2.11.20230323 is now available to upgrade and should resolve any such issues.

I've also enabled advanced SEF URLs on the K2 demo site here: demo.getk2.org/

downloads.joomla.org/technical-requirements mentions Joomla 3.x is compatible with PgSQL v9+. If you're talking about K2, we haven't had any reports of it not working with PgSQL.

So all I can say is, try in a staging environment to make sure all works as expected. If I were you I would upgrade Joomla to the latest 3.x release first.

This comes from your template overrides for K2 most likely (if not some other extension loading there in K2)...

The fix is easy, e.g. something like this: www.joomlaworks.net/forum/k2-en/59481-error-message-after-upgrade-to-php8-0-fpm#178585

I hope so; Joomla 3 support ends in August.

K2 is not yet ready for J4. Our plan is to release an update within the first half of 2023.

Same issue here
Jim

I want to upgrade from Joomla 3.10 to Joomla 4.26. However, the pre-update check gives me two errors. It says there is a potential upgrade issue with two K2 plugins:

System - K2
User - K2

How can I rectify this? Please help. 

there is error in k2.11 after upgrade to php8.0When I hit publish or unpublish button in k2 content
error : Attempt to assign property "id" on null
please review and help me to fix it

Hello.

after the last K2 upgrade, the following error appears:
0 count(): Argument #1 ($value) must be of type Countable|array, null given
/home/.../public_html/plugins/system/lscache/components/com_k2 . php:46

The error is only when saving and closing an article written in k2 or when clicking the close button.
When disabling the Litespeed plugin, the error disappears.

Last K2, Jomla 3, Litespeed plugin

What can be done?

This error comes from a K2 override or other Joomla module or plugin.

Open the Joomla debugger and switch error reporting to maximum to identify the exact origin of the error.

Hi, I update K2 installing the file downloaded from getk2.org/downloads/?f=K2_Rolling_Release.zip
but nothing change, in the blog page appear this error:

0 - count(): Argument #1 ($value) must be of type Countable|array, null given