It's not fully supported, no.

Carsten, if you want to fix this, please apply this solution: https://bugs.limesurvey.org/view.php?id=17105

Wait, a composer upgrade might be enough.

Hm, package sodium_compat is in the wrong folder.

hello @ollehar,
thanks for the quick reply!

yes, i think the issue of "Fatal error: Uncaught Error: Undefined constant "MB_OVERLOAD_STRING" which comes from sodium_compat is fixed by their developers already, so maybe you could upgrade your version if there are not any changes in the new sodium_compat that would break things in limesurvey.

Yeah, working on it, just have to move the package to our main vendor folder.

There are lots of errors of this kind:

function getSurveyUserList($bIncludeSuperAdmins = true, $surveyid)

Optional argument must be last. If you run with debug = 2, it might crash in a lot of places. So I'd recommend PHP 7.4 right now.

ok, great, thanks!

maybe just make sure when php 7.4 reaches end of security support that you atleast by then have the code compatible with php 8, thanks

For sure we want to support PHP 8 soon, but it's not considered a high-priority issue to get LS4 on our hosting platform.

If you want, you can checkout branch bug/17236-PHP-8-not-supported and test.

hello,
unfortunately i currently do not have the time to be involved in opensource projects currently.

maybe as a first step upgrade the sodium_compat library (and see if that breaks) anything so the new version is already there for the next limesurvey release and this part of an upgrade to php8 could be considered done?

Yes, I did upgrade sodium_compat. :) It's in branch bug/17236-PHP-8-not-supported. We'll test is before it gets merged into a release.

ok, thanks, great!

We had the same issue, but it took a while to figure it out because we only heard it from survey participants... If PHP 8 is not supported, it would be great if the application and/or the manual could warn me. https://manual.limesurvey.org/Installation_-_LimeSurvey_CE

Added a note to the manual, thanks for reminding us.

System used: PHP 8.0.1, 10.4.17-MariaDB on a recent Win10 XAMPP installation.
Managed to install and run version 4.6.0 (current "Unstable release") on PHP8.0.1 with the following changes:

limesurvey\installer\create-database.php: modifying (commenting out) the following lines
line 36: //$oTransaction = $oDB->beginTransaction();
line 1098: //$oTransaction->commit();
line 1100: //$oTransaction->rollback();

limesurvey\application\third_party\sodium_compat\src\Core\Util.php: inserted line 910
if (!defined('MB_OVERLOAD_STRING')) define('MB_OVERLOAD_STRING',2);

(see https://github.com/paragonie/sodium_compat/blob/master/src/Core/Util.php around line 900 where there is a note
Note: MB_OVERLOAD_STRING === 2, but we don't reference the constant (for nuisance-free PHP 8 support) etc.
also using
((int) (ini_get('mbstring.func_overload')) & 2);
a few lines later)

Please mind that this should be considered a QUICK FIX that helped to install lime survey on a localhost test server (therefore not checked in on
Testing the installation by creating a small sample survey worked so far, but do/did not have the time to test it in more details or add it on github (sorry).

First part (modifications for limesurvey\installer\create-database.php: commenting out lines) also helps for PHP8.0.1-support for LimeSurvey 3.26.2 -
note added see https://forums.limesurvey.org/forum/installation-a-update-issues/123515-noob-question-how-to-actually-install-limesurvey-on-pc.

We've made multiple patches to support PHP 8 on LS4, but they are still in a separate branch. Some libs require PHP 7.3 at least if you also want PHP 8 support, which screws with our PHP 7.0 compatibility. We might bump requirement to PHP 7.3 and release a LS5 version.

More details:

New minimum PHP requirement will be 7.2.5.
PHP8 support will be available with LS5.
The PHP8 branch is available at https://github.com/LimeSurvey/LimeSurvey/tree/bug/17236-PHP-8-not-supported

Fix committed to 3.x-LTS branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=31742

Release done.