docs(10_Wiki): Dev 폴더 누락분 반영 — Topic_Programming으로 통합

이전 재구성 작업에서 Dev/ 폴더가 누락되었던 것을 반영.

- Dev/Topic_Programming(중첩 폴더, 78개)은 Dev 자체 최상위 폴더들
  (Architecture/Conventions/Engineering_Intelligence 등)과 완전 중복이라 제거.
- Dev 최상위 엔지니어링 지식 폴더(Architecture/Conventions/Engineering_Intelligence/
  Failure_Library/Generalized_Principles/Language/Pattern_Catalog/Platform_Guides/
  Subsystems, 77개)는 이미 Topic_Programming/Topic_Programming에 더 최신 버전이
  존재해 중복 제거(고유 콘텐츠 1개는 예외 처리하여 이동 보존).
- Dev의 W3Schools 언어 튜토리얼 폴더(Topic_C/CPP/CSS/CSharp/HOWTO/HTML/Java/
  JavaScript/PHP/Python/SQL/W3CSS, 1201개)는 전부 Topic_Programming 하위로 이동.
- 에이전트 운영 상태(.astra/docs)는 그대로 유지, 콘텐츠 폴더만 정리.
- Topic_Programming 최종 문서 수: 2784 → 3985.

10_Wiki/Topic_Programming/Topic_PHP/PHP_Sessions.md

@@ -0,0 +1,75 @@
+---
+id: php-sessions
+title: "PHP Sessions"
+category: "Programming_Language"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["session_start()", "$_SESSION", "PHP 세션"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.9
+created_at: 2026-07-04
+updated_at: 2026-07-04
+review_reason: ""
+merge_history: []
+tags: ["php", "programming", "w3schools", "sessions"]
+raw_sources: ["https://www.w3schools.com/php/php_sessions.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[PHP Sessions]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+A session's ONLY client-side footprint is a small random ID stored in a `PHPSESSID` cookie — the actual session DATA lives entirely on the server (typically in a temp file), meaning sessions are fundamentally more secure than cookies for sensitive data, since the browser never holds the real information, just a lookup key. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Session** — solves HTTP's statelessness by storing per-user data server-side, linked via a client-side ID cookie. [S1]
+- **`session_start()`** — must be called at the very beginning of every script using sessions, before ANY HTML output or whitespace. [S1]
+- **`$_SESSION`** — superglobal for storing/accessing session variables. [S1]
+- **`unset($_SESSION["key"])`** — removes one session variable. [S1]
+- **`session_unset()`** — clears ALL session variables. [S1]
+- **`session_destroy()`** — destroys all data tied to the current session entirely. [S1]
+- **Default lifetime** — session data persists until the browser closes (unlike cookies, which can have a long fixed expiration). [S1]
+- **Sessions vs. cookies** — sessions: server-stored, more secure, closes-on-browser-close, more efficient (no repeated data transfer); cookies: browser-stored, less secure, long expiration possible, less efficient (sent with every request). [S1]
+
+## 📖 세부 내용 (Details)
+- Start + set variables: `session_start(); $_SESSION["favcolor"] = "green"; $_SESSION["favanimal"] = "cat";`. [S1]
+- Retrieve on another page: `session_start(); if(isset($_SESSION["favcolor"])) { echo $_SESSION["favcolor"]; }`. [S1]
+- Modify: overwrite directly — `$_SESSION["favcolor"] = "yellow";`. [S1]
+- Destroy (logout): `session_start(); session_unset(); session_destroy(); echo "You have been logged out.";`. [S1]
+- Debug all values: `print_r($_SESSION);`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — session_unset()+session_destroy() 조합으로 로그아웃을 구현하는 것이 실전 인증 시스템의 표준 패턴이다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Logging out by clearing all session data (PHP):
+```php
+session_start();
+session_unset();
+session_destroy();
+echo "You have been logged out.";
+```
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.90
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[PHP Tutorial]]
+- **관련 개념:** [[PHP Cookies]], [[PHP Filter]]
+- **참조 맥락:** 서버 측 사용자 데이터 저장 — 필터(Filter) 섹션으로 이어짐.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — PHP Sessions — https://www.w3schools.com/php/php_sessions.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "PHP Sessions" page (Astra wiki-curation, P-Reinforce v3.1 format).