update default.nix

default.nix

@@ -1,6 +1,10 @@
 { pkgs ? import <nixpkgs> {} }:
 with pkgs;
 {
+  phpPack = import ./php-packages.nix {
+      inherit composerEnv noDev;
+      inherit (pkgs) fetchurl fetchgit fetchhg fetchsvn;
+  };
   source = stdenv.mkDerivation {
       name = "searchanddisplace-core-source";
       src = builtins.fetchGit {