2nd/10_Wiki/Dev/Topic_PHP/PHP_Exception.md

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id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
php-exception	PHP Exception	Programming_Language	draft	conceptual		custom exception class re-throwing set_exception_handler PHP 예외 처리 심화		B	0.9	2026-07-04	2026-07-04			php programming w3schools exceptions oop	https://www.w3schools.com/php/php_exception.asp

PHP Exception

🎯 한 줄 통찰 (One-line insight)

Re-throwing an exception requires nesting a try block INSIDE another try block — the inner try catches the raw system exception, then throws a new user-friendly customException in its own catch block, which the OUTER catch finally handles; this two-layer structure is how PHP lets you translate an internal error into a message safe to show end users. [S1]

🧠 핵심 개념 (Core concepts)

• Custom exception class — must extends Exception; inherits getLine(), getFile(), getMessage(), and can add custom methods. [S1]
• Multiple exceptions — a try block can have MULTIPLE catch blocks for different exception classes; PHP matches the first applicable one. [S1]
• Re-throwing — nesting a try/catch inside another try, so a caught exception can be replaced with a different (often more user-friendly) one before reaching the outer catch. [S1]
• set_exception_handler($functionName) — installs a top-level handler that catches ANY exception with no matching catch block anywhere. [S1]
• Core rule — "If you throw something, you have to catch it" — every throw needs at least one corresponding catch (or a top-level handler as the ultimate fallback). [S1]

📖 세부 내용 (Details)

• Custom exception class: class customException extends Exception { public function errorMessage() { return 'Error on line '.$this->getLine().' in '.$this->getFile().': '.$this->getMessage().' is not a valid E-Mail address'; } }. [S1]
• Using it: try { if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE) { throw new customException($email); } } catch (customException $e) { echo $e->errorMessage(); }. [S1]
• Multiple catch blocks for different conditions: try { if(...) { throw new customException($email); } if(strpos($email, "example") !== FALSE) { throw new Exception("$email is an example e-mail"); } } catch (customException $e) { ... } catch(Exception $e) { ... }. [S1]
• Re-throwing pattern: try { try { if(strpos($email, "example") !== FALSE) { throw new Exception($email); } } catch(Exception $e) { throw new customException($email); } } catch (customException $e) { echo $e->errorMessage(); }. [S1]
• Top-level handler: function myException($exception) { echo "Exception: " . $exception->getMessage(); } set_exception_handler('myException'); throw new Exception('Uncaught Exception occurred');. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 재발생(re-throw)의 이중 try 구조: 원본 시스템 에러를 사용자 친화적 메시지로 바꾸려면 try 블록 안에 또 다른 try 블록을 중첩해야 한다는 구조적 필요성이 예제로 명확히 드러남. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 이메일 형식 오류를 커스텀 예외 클래스로 감싸 사용자 친화적 메시지를 보여주는 것이 실전 예외 설계의 대표 사례다. [S1]

💻 코드 패턴 (Code patterns)

Re-throwing a system exception as a user-friendly custom exception (PHP):

class customException extends Exception {
    public function errorMessage() {
        return $this->getMessage() . ' is not a valid E-Mail address.';
    }
}
try {
    try {
        if (strpos($email, "example") !== FALSE) {
            throw new Exception($email);
        }
    } catch (Exception $e) {
        throw new customException($email); // re-throw as friendlier exception
    }
} catch (customException $e) {
    echo $e->errorMessage();
}

✅ 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 Exceptions, PHP Error Handling, PHP OOP Inheritance
• 참조 맥락: 커스텀 예외 클래스와 상속 — OOP 섹션의 상속(Inheritance) 개념과 직접 연결됨.

📚 출처 (Sources)

• [S1] W3Schools — PHP Exception Handling — https://www.w3schools.com/php/php_exception.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "PHP Exception Handling" page (Astra wiki-curation, P-Reinforce v3.1 format).