{
  description = "A reproducible PHP 5.6 development environment";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    phps.url = "github:fossar/nix-phps";
  };

  outputs = { self, nixpkgs, phps, ... }: {
    devShell.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.mkShell {
      buildInputs = [
        phps.packages.x86_64-linux.php56
      ];
    };
  };
}

error: Cannot build '/nix/store/hnv4hq4dwmj4pm8173qd2jrnahila196-php-ldap-5.6.40.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/l38k2zfz9ym093h8qf81f1afrqnqih8p-php-ldap-5.6.40-dev
         /nix/store/rb1lpgrq1f8v1sxzhb5a3fc35w7a1gbb-php-ldap-5.6.40
       Last 25 log lines:
       > checking for re2c... re2c
       > checking for re2c version... 4.3 (ok)
       > checking for gawk... gawk
       > checking for LDAP support... yes, shared
       > checking for LDAP Cyrus SASL support... /nix/store/j81r2hhasz3g4ydw9dmi2w5ch0cwk3vw-cyrus-sasl-2.1.28-dev
       > checking for stdio.h... yes
       > checking for stdlib.h... yes
       > checking for string.h... yes
       > checking for inttypes.h... yes
       > checking for stdint.h... yes
       > checking for strings.h... yes
       > checking for sys/stat.h... yes
       > checking for sys/types.h... yes
       > checking for unistd.h... yes
       > checking size of long int... 8
       > checking for stdio.h... (cached) yes
       > checking for stdlib.h... (cached) yes
       > checking for string.h... (cached) yes
       > checking for inttypes.h... (cached) yes
       > checking for stdint.h... (cached) yes
       > checking for strings.h... (cached) yes
       > checking for sys/stat.h... (cached) yes
       > checking for sys/types.h... (cached) yes
       > checking for unistd.h... (cached) yes
       > configure: error: Cannot find ldap libraries in /usr/lib.
       For full logs, run:
         nix log /nix/store/hnv4hq4dwmj4pm8173qd2jrnahila196-php-ldap-5.6.40.drv
error: Cannot build '/nix/store/gfp4f5h5prpkcxmd9vxvs78nacrvkfsm-php-extra-init-5.6.40.ini.drv'.
       Reason: 1 dependency failed.
       Output paths:
         /nix/store/hypjhglk74jgc0pa99g9fc6iig6l5fi6-php-extra-init-5.6.40.ini
error: Cannot build '/nix/store/6xbqv7k13zhd228s9vmg964xkd86hwg3-php-with-extensions-5.6.40.drv'.
       Reason: 1 dependency failed.
       Output paths:
         /nix/store/crg1c5kvb7yprhajkq3xcm9hdl19dnhh-php-with-extensions-5.6.40
error: Cannot build '/nix/store/3jyz4kprjddhj7dxv00i6d8j8jyn90dl-nix-shell-env.drv'.
       Reason: 1 dependency failed.
       Output paths:
         /nix/store/pdlsapkzma2xpkm58ka8bhpnvvxpmk8h-nix-shell-env