JIT: isset/empty on runtime-populated sg_GET keys (close #49 JIT slice)

[PurHur]

Problem

#49 umbrella remains open for JIT paths where SuperglobalInit still folds literal keys at compile time. #70 / #86 closed literal-key isset; apps using dynamic keys still fail JIT:

$key = 'name';
if (isset($_GET[$key])) { echo $_GET[$key]; }

IssetHelper / lib/JIT/Builtin/IssetHelper.php must call __hashtable__offsetIsSet on sg_GET / sg_POST when the key is non-constant.

Goal

• isset($_GET[$var]) and empty($_GET[$var]) compile under JIT when superglobals are runtime-filled (JIT: Per-run superglobal refresh for bin/jit.php (-q/-p between invocations) #642 per-run refresh)
• PHPT: test/compliance/cases/web/web_isset_dynamic_get_jit.phpt
• Narrow Web: Runtime-populated superglobals for JIT and AOT (per-request $_GET/$_POST) #49 — close JIT slice when AOT + JIT dynamic isset both green

Implementation hints

Layer	Files
Isset	lib/JIT/Builtin/IssetHelper.php
Empty	lib/JIT.php empty lowering
Tests	test/aot/JitSuperglobalRefreshTest.php
AOT	already linked superglobals_refresh.c

Acceptance criteria

./script/ci-local.sh --filter 'web_isset_dynamic|JitSuperglobal'
php bin/jit.php -q 'name=Alice' -r 'echo isset($_GET["name"]) ? $_GET["name"] : "no";'
# → Alice (key via variable index)

Verification (local / Docker only)

docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  ./script/ci-local.sh --filter JitSuperglobal

Dependencies

• Web: Runtime-populated superglobals for JIT and AOT (per-request $_GET/$_POST) #49 — parent; close when JIT + docs updated
• JIT: Per-run superglobal refresh for bin/jit.php (-q/-p between invocations) #642 ✅ — per-run JIT refresh
• Web: JIT/AOT mode for bin/serve.php (compile per script on first request) #207 — serve --jit consumer

Links

• Closed: Web: Dynamic isset/empty on $_GET and $_POST keys in JIT #70, JIT: Dynamic hashtable read/write for $_GET[$key] and $_POST[$key] #86
• ROADMAP #78 Phase 3