feat(php-rpc): query real PHP version and binary for --version

Add a minimal shirabe-php-rpc crate that spawns the system PHP as a
child process and asks it for runtime information over a Unix domain
socket, then use it to fill the `--version` PHP line with the real
\PHP_VERSION and \PHP_BINARY instead of fixed placeholder values.

See docs/dev/php-rpc.md for the design and scope.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

3 files changed, 157 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/Cargo.toml b/crates/shirabe-php-rpc/Cargo.toml
new file mode 100644
index 0000000..692dda9
--- /dev/null
+++ b/crates/shirabe-php-rpc/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "shirabe-php-rpc"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+shirabe-external-packages.workspace = true
+tempfile.workspace = true
+
+[lints]
+workspace = true
diff --git a/crates/shirabe-php-rpc/php/worker.php b/crates/shirabe-php-rpc/php/worker.php
new file mode 100644
index 0000000..214817a
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/worker.php
@@ -0,0 +1,37 @@
+<?php
+
+// PHP glue worker. See docs/dev/php-rpc.md.
+
+$client = @stream_socket_client('unix://' . $argv[1], $errno, $errstr);
+if ($client === false) {
+    exit(1);
+}
+$dispatch = [
+    'get_php_version' => static fn() => PHP_VERSION,
+    'get_php_binary'  => static fn() => PHP_BINARY,
+];
+$read_exact = static function ($conn, int $len): ?string {
+    $buf = '';
+    while (strlen($buf) < $len) {
+        $chunk = fread($conn, $len - strlen($buf));
+        if ($chunk === false || $chunk === '') {
+            return null;
+        }
+        $buf .= $chunk;
+    }
+    return $buf;
+};
+while (true) {
+    $header = $read_exact($client, 8);
+    if ($header === null) {
+        break;
+    }
+    $len = unpack('P', $header)[1];
+    $name = $len === 0 ? '' : $read_exact($client, $len);
+    if ($name === null) {
+        break;
+    }
+    $result = isset($dispatch[$name]) ? ($dispatch[$name])() : null;
+    $payload = serialize($result);
+    fwrite($client, pack('P', strlen($payload)) . $payload);
+}
diff --git a/crates/shirabe-php-rpc/src/lib.rs b/crates/shirabe-php-rpc/src/lib.rs
new file mode 100644
index 0000000..f08a79a
--- /dev/null
+++ b/crates/shirabe-php-rpc/src/lib.rs
@@ -0,0 +1,109 @@
+//! Rust-to-PHP RPC over a Unix domain socket. See `docs/dev/php-rpc.md`.
+
+use shirabe_external_packages::symfony::process::PhpExecutableFinder;
+use std::io::{Read, Write};
+use std::os::unix::net::{UnixListener, UnixStream};
+use std::sync::{LazyLock, Mutex};
+use std::time::{Duration, Instant};
+
+/// PHP `\PHP_VERSION`.
+pub fn get_php_version() -> String {
+    call("get_php_version").unwrap_or_default()
+}
+
+/// PHP `\PHP_BINARY`.
+pub fn get_php_binary() -> String {
+    call("get_php_binary").unwrap_or_default()
+}
+
+const GLUE_SCRIPT: &str = include_str!("../php/worker.php");
+
+struct Worker {
+    stream: UnixStream,
+    // Kept alive for the process lifetime: the child interpreter and the temp dir holding the socket
+    // and glue script. Neither is dropped because the worker lives in a never-dropped static.
+    _child: std::process::Child,
+    _tempdir: tempfile::TempDir,
+}
+
+impl Worker {
+    fn request(&mut self, name: &str) -> Option<String> {
+        write_frame(&mut self.stream, name.as_bytes()).ok()?;
+        let payload = read_frame(&mut self.stream).ok()?;
+        parse_serialized_string(&payload)
+    }
+}
+
+static WORKER: LazyLock<Mutex<Option<Worker>>> = LazyLock::new(|| Mutex::new(spawn_worker()));
+
+fn call(name: &str) -> Option<String> {
+    let mut guard = WORKER.lock().ok()?;
+    guard.as_mut()?.request(name)
+}
+
+fn spawn_worker() -> Option<Worker> {
+    let php = PhpExecutableFinder::new().find(false)?;
+
+    let tempdir = tempfile::tempdir().ok()?;
+    let socket_path = tempdir.path().join("rpc.sock");
+    let script_path = tempdir.path().join("worker.php");
+    std::fs::write(&script_path, GLUE_SCRIPT).ok()?;
+
+    // Bind before spawning so the socket exists when the child connects.
+    let listener = UnixListener::bind(&socket_path).ok()?;
+    listener.set_nonblocking(true).ok()?;
+
+    let child = std::process::Command::new(&php)
+        .arg(&script_path)
+        .arg(&socket_path)
+        .spawn()
+        .ok()?;
+
+    // Poll for the child's connection with a bounded deadline so a child that never connects does
+    // not hang the caller.
+    let deadline = Instant::now() + Duration::from_secs(10);
+    let stream = loop {
+        match listener.accept() {
+            Ok((stream, _)) => break stream,
+            Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
+                if Instant::now() >= deadline {
+                    return None;
+                }
+                std::thread::sleep(Duration::from_millis(5));
+            }
+            Err(_) => return None,
+        }
+    };
+    stream.set_nonblocking(false).ok()?;
+
+    Some(Worker {
+        stream,
+        _child: child,
+        _tempdir: tempdir,
+    })
+}
+
+fn write_frame(stream: &mut UnixStream, payload: &[u8]) -> std::io::Result<()> {
+    stream.write_all(&(payload.len() as u64).to_le_bytes())?;
+    stream.write_all(payload)?;
+    stream.flush()
+}
+
+fn read_frame(stream: &mut UnixStream) -> std::io::Result<Vec<u8>> {
+    let mut header = [0u8; 8];
+    stream.read_exact(&mut header)?;
+    let len = u64::from_le_bytes(header) as usize;
+    let mut payload = vec![0u8; len];
+    stream.read_exact(&mut payload)?;
+    Ok(payload)
+}
+
+/// Parse the `s:<len>:"<bytes>";` form; only strings are needed here, so other forms are rejected.
+fn parse_serialized_string(payload: &[u8]) -> Option<String> {
+    let rest = payload.strip_prefix(b"s:")?;
+    let colon = rest.iter().position(|&b| b == b':')?;
+    let len: usize = std::str::from_utf8(&rest[..colon]).ok()?.parse().ok()?;
+    let after = rest.get(colon + 1..)?;
+    let bytes = after.strip_prefix(b"\"")?.get(..len)?;
+    Some(String::from_utf8_lossy(bytes).into_owned())
+}