feat: add PHP environment

php/.envrc

@@ -0,0 +1 @@
+use flake .

php/flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1659877975,
+        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1664349153,
+        "narHash": "sha256-F6ZAHd9qR2lp49L1NiBFZ1NVJdTne56+dkI62glOj/w=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "467132e5ab10f122fbe313ebcc31eeaca65fae42",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

php/flake.nix

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+{
+  description = "A Nix-flake-based PHP development environment";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs";
+  };
+
+  outputs =
+    { self
+    , flake-utils
+    , nixpkgs
+    }:
+
+    flake-utils.lib.eachDefaultSystem (system:
+    let
+      overlays = [
+        (self: super: rec {
+          php = super.php;
+          composer = super.phpPackages.composer;
+        })
+      ];
+      pkgs = import nixpkgs { inherit overlays system; };
+    in
+    {
+      devShell = pkgs.mkShell {
+        buildInputs = with pkgs; [ composer php ];
+
+        shellHook = ''
+          echo "`${pkgs.php}/bin/php --version`"
+        '';
+      };
+    });
+}