Add composer2nix to all PHP dev shells

flake.nix

@@ -1,5 +1,8 @@
 {
   inputs = {
+    composer2nix.flake = false;
+    composer2nix.url = "github:svanderburg/composer2nix";
+
     devshell.inputs.nixpkgs.follows = "nixpkgs";
     devshell.url = "github:numtide/devshell";
 
@@ -19,7 +22,16 @@
       systems = [ "x86_64-linux" ];
 
       _module.args = {
-        commonPhpPackages = pkgs: with pkgs; [ phpactor ];
+        commonPhpPackages =
+          pkgs: system:
+          with pkgs;
+          let
+            composer2nix = import inputs.composer2nix { inherit system pkgs; };
+          in
+          [
+            composer2nix
+            phpactor
+          ];
       };
 
       imports = [