There is now a PHP label, so lets have them added automatically for us :)

https://github.com/NixOS/nixpkgs/pull/295643

In reply to @drupol:matrix.org
tgerbet: Are you ok with this? ^^ Eval is red, but that's because of the warning. How to deal with that in nixpkgs?

In reply to @tgerbet:matrix.org
I do not think lib.warnIf can be used for that. It will always be flagged by the nix-instantiate call done by OfBorg and it is not really an issue within nixpkgs code itself but from upstreams.

 engelsystem-migrate-start[1012]: Exception: Code: 0, Message: Call to undefined function Symfony\Polyfill\Mbstring\iconv_substr(), File: vendor/symfony/polyfill-mbstring/Mbstring.php:660, Previous: None, Trace: [{"file":"\/nix\/store\/03xgnc2nzf5z0112j4b1kmm5qpyrapqf-engelsystem-3.5.0\/share\/engelsystem\/vendor\/symfony\/polyf]

Something like this should do the trick

diff --git a/nixos/modules/services/web-apps/engelsystem.nix b/nixos/modules/services/web-apps/engelsystem.nix
index 669620debce5..7fb912415643 100644
--- a/nixos/modules/services/web-apps/engelsystem.nix
+++ b/nixos/modules/services/web-apps/engelsystem.nix
@@ -3,6 +3,8 @@
 let
   inherit (lib) mkDefault mkEnableOption mkIf mkOption types mkPackageOption;
   cfg = config.services.engelsystem;
+  phpExt = pkgs.php.withExtensions
+    ({ enabled, all }: with all; [ filter mysqlnd mysqli pdo pdo_mysql mbstring ] ++ enabled);
 in {
   options = {
     services.engelsystem = {
@@ -99,7 +101,7 @@ in {
       '';
 
     services.phpfpm.pools.engelsystem = {
-      phpPackage = pkgs.php81;
+      phpPackage = phpExt;
       user = "engelsystem";
       settings = {
         "listen.owner" = config.services.nginx.user;
diff --git a/pkgs/servers/web-apps/engelsystem/default.nix b/pkgs/servers/web-apps/engelsystem/default.nix
index 9b9cf0ff3bfe..8274f3e88418 100644
--- a/pkgs/servers/web-apps/engelsystem/default.nix
+++ b/pkgs/servers/web-apps/engelsystem/default.nix
@@ -2,15 +2,15 @@
 
 let
   phpExt = php.withExtensions
-    ({ enabled, all }: with all; [ filter mysqlnd mysqli pdo pdo_mysql ]);
+    ({ enabled, all }: with all; [ filter mysqlnd mysqli pdo pdo_mysql mbstring ] ++ enabled);
 in
 stdenv.mkDerivation rec {
   pname = "engelsystem";
-  version = "3.4.1";
+  version = "3.5.0";
 
   src = fetchzip {
     url = "https://github.com/engelsystem/engelsystem/releases/download/v${version}/engelsystem-v${version}.zip";
-    hash = "sha256-5KniP1nrLfmWHruXnUJmlvgL95U+EsDmCs4tg/YLWtw=";
+    hash = "sha256-RbzAHBZN02u14WaLtq5EOh4XwIdHKvzX7NhDBhn/CaU=";
   };
 
   buildInputs = [ phpExt ];
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 1f6edde48394..acd7f66f5b61 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -25999,7 +25999,7 @@ with pkgs;
 
   dspam = callPackage ../servers/mail/dspam { };
 
-  engelsystem = callPackage ../servers/web-apps/engelsystem { php = php81; };
+  engelsystem = callPackage ../servers/web-apps/engelsystem { };
 
   envoy = callPackage ../servers/http/envoy {
     go = go_1_20;