Closes #83 #880 #1286.

Working patch for Windows support.

Supports linking to the [official PHP release (TS
version)](https://www.php.net/downloads.php).
Includes some work from #1286 (thanks @TenHian!!)

This patch allows using Visual Studio to compile the cgo code. To do so,
it must be compiled with Go 1.26 (RC) with the following setup:

```powershell
winget install -e --id Microsoft.VisualStudio.2022.Community --override "--passive --wait --add Microsoft.VisualStudio.Workload.NativeDesktop --add Microsoft.VisualStudio.Component.VC.Llvm.Clang --includeRecommended"
winget install -e --id GoLang.Go

$env:PATH += ';C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\Llvm\bin'

cd c:\
gh repo clone microsoft/vcpkg
.\vcpkg\bootstrap-vcpkg.bat
.\vcpkg\vcpkg install pthreads brotli

# build watcher
Invoke-WebRequest -Uri "https://github.com/e-dant/watcher/releases/download/0.14.3/x86_64-pc-windows-msvc.tar" -OutFile "$env:TEMP\watcher.tar"
tar -xf "$env:TEMP\watcher.tar" -C C:\
Rename-Item -Path "C:\x86_64-pc-windows-msvc" -NewName "watcher-x86_64-pc-windows-msvc"
Remove-Item "$env:TEMP\watcher.tar"

# download php
Invoke-WebRequest -Uri "https://downloads.php.net/~windows/releases/archives/php-8.5.1-Win32-vs17-x64.zip" -OutFile "$env:TEMP\php.zip"
Expand-Archive -Path "$env:TEMP\php.zip" -DestinationPath "C:\"
Remove-Item "$env:TEMP\php.zip"

# download php development package
Invoke-WebRequest -Uri "https://downloads.php.net/~windows/releases/archives/php-devel-pack-8.5.1-Win32-vs17-x64.zip" -OutFile "$env:TEMP\php-devel.zip"
Expand-Archive -Path "$env:TEMP\php-devel.zip" -DestinationPath "C:\"
Remove-Item "$env:TEMP\php-devel.zip"

$env:GOTOOLCHAIN = 'go1.26rc1'
$env:CC = 'clang'
$env:CXX = 'clang++'
$env:CGO_CFLAGS = "-I$env:C:\vcpkg\installed\x64-windows\include -IC:\watcher-x86_64-pc-windows-msvc -IC:\php-8.5.1-devel-vs17-x64\include -IC:\php-8.5.1-devel-vs17-x64\include\main -IC:\php-8.5.1-devel-vs17-x64\include\TSRM -IC:\php-8.5.1-devel-vs17-x64\include\Zend -IC:\php-8.5.1-devel-vs17-x64\include\ext"
$env:CGO_LDFLAGS = '-LC:\vcpkg\installed\x64-windows\lib -lbrotlienc -LC:\watcher-x86_64-pc-windows-msvc -llibwatcher-c -LC:\php-8.5.1-Win32-vs17-x64 -LC:\php-8.5.1-devel-vs17-x64\lib -lphp8ts -lphp8embed'

# clone frankenphp and build
git clone -b windows https://github.com/php/frankenphp.git
cd frankenphp\caddy\frankenphp
go build -ldflags '-extldflags="-fuse-ld=lld"' -tags nowatcher,nobadger,nomysql,nopgx

# Tests

$env:PATH += ";$env:VCPKG_ROOT\installed\x64-windows\bin;C:\watcher-x86_64-pc-windows-msvc";C:\php-8.5.1-Win32-vs17-x64"
"opcache.enable=0`r`nopcache.enable_cli=0" | Out-File -Encoding ascii php.ini
$env:PHPRC = Get-Location
go test -ldflags '-extldflags="-fuse-ld=lld"' -tags nowatcher,nobadger,nomysql,nopgx .
```

TODO:

- [x] Fix remaining skipped tests (scaling and watcher)
- [x] Test if the watcher mode works as expected
- [x] Automate the build with GitHub Actions

---------

Signed-off-by: Marc <[email protected]>
Co-authored-by: Kévin Dunglas <[email protected]>
Co-authored-by: DubbleClick <[email protected]>

This PR uses `zend_array_dup` to simplify and optimize the environment sandboxing
logic. It also guarantees no environment leakage on FrankenPHP restarts.

Adds `XDG_CONFIG_HOME` and `XDG_DATA_HOME` to the example hardened image
docs, otherwise Caddy will fail to use the nonexistent /home directory
instead of `/data/caddy` and `/config/caddy`.

Also removes an unnecessary `--chown=nonroot:nonroot`.

Update the shell script and add a PowerShell script to install the
Windows binary.

---------

Co-authored-by: Kévin Dunglas <[email protected]>

Prevent crashes when `php.ini` references PHP extensions using relative
paths, and FrankenPHP is started from a different working directory than
the one containing extensions, or with `caddy start` (instead of `caddy
run`).

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

Signed-off-by: Kévin Dunglas <[email protected]>
Co-authored-by: Copilot <[email protected]>

Introduces C-side interned string registry (frankenphp_strings) and a frankenphp_server_vars struct to bulk-register known $_SERVER variables with pre-sized hashtable capacity.

Unfortunately, GitHub Actions is often blocked by the php.net CDN. This
patch adds a fallback to use GitHub to try to determine the PHP version
to use. This is less ideal because PHP currently doesn't use GitHub
extensively, and distribution archives aren't available in the GitHub
releases, only on php.net.

Signed-off-by: Kévin Dunglas <[email protected]>
Co-authored-by: Copilot <[email protected]>

Add configurable max_idle_time for autoscaled threads

The idle timeout for autoscaled threads is currently hardcoded to 5
seconds. With bursty traffic patterns, this causes threads to be
deactivated too quickly, leading to repeated cold-start overhead when
the next burst arrives.

This PR replaces the hardcoded constant with a configurable
max_idle_time directive, allowing users to tune how long idle
autoscaled threads stay alive before deactivation. The default remains 5
seconds, preserving existing behavior.

  Usage:

  Caddyfile:
````
  frankenphp {
      max_idle_time 30s
  }
````
  JSON config:
```
  {
      "frankenphp": {
          "max_idle_time": "30s"
      }
  }
````

  Changes:
  - New max_idle_time Caddyfile directive and JSON config option
  - New WithMaxIdleTime functional option
- Replaced hardcoded maxThreadIdleTime constant with configurable
maxIdleTime variable
  - Added tests for custom and default idle time behavior
  - Updated docs