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10_Wiki/Dev/Topic_PHP/PHP_Casting.md

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+---
+id: php-casting
+title: "PHP Casting"
+category: "Programming_Language"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["type casting", "PHP 타입 캐스팅"]
+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", "casting", "types"]
+raw_sources: ["https://www.w3schools.com/php/php_casting.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[PHP Casting]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Casting an object to an array converts its property names into array keys automatically (`(array) $myCar` turns `color`/`model` properties into `["color" => ..., "model" => ...]`) — this reversible object↔associative-array relationship is a core mechanic for interoperating between OOP and plain data structures in PHP. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Casting operators** — `(string)`, `(int)`, `(float)`, `(bool)`, `(array)`, `(object)`, `(unset)` (deprecated in 7.2, removed in 8.0). [S1]
+- **Bool cast rule** — `0`, `NULL`, `false`, `""` (empty string) convert to `false`; everything else (even `-1`) converts to `true`. [S1]
+- **Array cast on scalars** — most types become a single-element indexed array. [S1]
+- **Array cast on objects** — becomes an associative array with property names as keys. [S1]
+- **Object cast on scalars** — becomes an object with one property named `"scalar"`. [S1]
+- **Object cast on arrays** — indexed arrays get numeric-index property names; associative arrays keep their keys as property names. [S1]
+- **NULL casting** — the deprecated/removed `(unset)` operator is replaced by simply assigning `NULL` directly. [S1]
+
+## 📖 세부 내용 (Details)
+- Bool falsy values: `$c = 0; $g = ""; // both cast to false`, while `$d = -1; // casts to true`. [S1]
+- Object → array: `class Car { public $color; public $model; ... } $myCar = new Car("red", "Volvo"); $myCar = (array) $myCar; var_dump($myCar); // ["color" => "red", "model" => "Volvo"]`. [S1]
+- Indexed array → object: `$a = array("Volvo", "BMW", "Toyota"); $a = (object) $a; // properties named 0, 1, 2`. [S1]
+- Associative array → object: `$b = array("Peter"=>"35", "Ben"=>"37"); $b = (object) $b; // properties named Peter, Ben`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+- **(unset) 캐스팅 지원 중단**: PHP 7.2.0에서 지원 중단(deprecated), PHP 8.0.0에서 완전히 제거됨 — 대신 변수에 NULL을 직접 할당하는 방식 사용. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 객체를 연관 배열로 변환하는 패턴이 데이터 직렬화/디버깅에서 자주 쓰인다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Casting an object to an associative array (PHP):
+```php
+class Car {
+    public $color;
+    public $model;
+    public function __construct($color, $model) {
+        $this->color = $color;
+        $this->model = $model;
+    }
+}
+$myCar = new Car("red", "Volvo");
+$myCar = (array) $myCar;
+var_dump($myCar); // ["color" => "red", "model" => "Volvo"]
+```
+
+## ✅ 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 Numbers]], [[PHP Data Types]], [[PHP OOP Classes Objects]], [[PHP Arrays]]
+- **참조 맥락:** 명시적 타입 변환 — 수학함수(Math) 챕터로 이어짐.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — PHP Type Casting — https://www.w3schools.com/php/php_casting.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "PHP Type Casting" page (Astra wiki-curation, P-Reinforce v3.1 format).