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.
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+---
+id: php-oop-inheritance
+title: "PHP OOP Inheritance"
+category: "Programming_Language"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["extends", "final keyword", "PHP 상속"]
+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", "oop", "inheritance"]
+raw_sources: ["https://www.w3schools.com/php/php_oop_inheritance.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[PHP OOP Inheritance]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Calling a `protected` method from OUTSIDE the class fails, but calling that SAME protected method from WITHIN a subclass's own method (via `$this->intro()`) succeeds — the exact rule from access modifiers applies identically to methods, and the source proves it with a direct pass/fail comparison of the two call sites. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **`extends`** — inherits public and protected properties/methods from a parent class. [S1]
+- **Private members are NOT inherited** — a child class cannot access a parent's private methods/properties at all. [S1]
+- **Method overriding** — redefining a method with the same name in the child class replaces the parent's version. [S1]
+- **`final` on a class** — prevents any class from extending it. [S1]
+- **`final` on a method** — prevents child classes from overriding that specific method. [S1]
+
+## 📖 세부 내용 (Details)
+- Basic inheritance: `class Fruit { public $name; public $color; public function __construct($name, $color) {...} public function intro() {...} } class Strawberry extends Fruit { public function message() {...} } $strawberry = new Strawberry("Strawberry", "red"); $strawberry->intro(); $strawberry->message();` — Strawberry uses Fruit's constructor/intro plus its own message(). [S1]
+- Protected method fails from outside: `$strawberry->intro(); // ERROR if intro() is protected`. [S1]
+- Protected method works from inside a child method: `public function message() { $this->intro(); }` — calling `$this->intro()` from within `message()` succeeds. [S1]
+- Overriding: child class `Strawberry` redefines `__construct()` and `intro()` with the same names, completely replacing the parent's versions (adding a `$weight` property along the way). [S1]
+- `final` prevents inheritance: `final class Fruit {...} class Strawberry extends Fruit {...} // error`. [S1]
+- `final` prevents method override: `class Fruit { final public function intro() {...} } class Strawberry extends Fruit { public function intro() {...} // error }`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+- **protected 메서드 호출 위치에 따른 성패**: 클래스 외부에서 호출하면 에러, 파생 클래스 내부 메서드에서 $this로 호출하면 성공한다는 점이 두 대비 예제로 직접 증명됨. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — Strawberry가 Fruit의 생성자/메서드를 재정의(override)하며 weight 속성을 추가하는 것이 실전 오버라이딩의 대표 사례다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Overriding a parent's constructor and method (PHP):
+```php
+class Fruit {
+    public $name;
+    public $color;
+    public function __construct($name, $color) { $this->name = $name; $this->color = $color; }
+    public function intro() { echo "The fruit is $this->name and the color is $this->color."; }
+}
+class Strawberry extends Fruit {
+    public $weight;
+    public function __construct($name, $color, $weight) {
+        $this->name = $name; $this->color = $color; $this->weight = $weight;
+    }
+    public function intro() {
+        echo "A $this->name is $this->color, and the weight is $this->weight gram.";
+    }
+}
+```
+
+## ✅ 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 OOP Access Modifiers]], [[PHP OOP Constants]], [[PHP OOP Classes Abstract]]
+- **참조 맥락:** 클래스 상속과 메서드 오버라이딩 — 클래스 상수(Constants) 챕터로 이어짐.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — PHP OOP - Inheritance — https://www.w3schools.com/php/php_oop_inheritance.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "PHP OOP Inheritance" page (Astra wiki-curation, P-Reinforce v3.1 format).