---
id: php-exception
title: "PHP Exception"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["custom exception class", "re-throwing", "set_exception_handler", "PHP 예외 처리 심화"]
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", "exceptions", "oop"]
raw_sources: ["https://www.w3schools.com/php/php_exception.asp"]
applied_in: []
github_commit: ""
---

# [[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):
```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).