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10_Wiki/Dev/Topic_PHP/PHP_Form_Required.md

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+---
+id: php-form-required
+title: "PHP Form Required"
+category: "Programming_Language"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["empty()", "PHP 필수 필드"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.89
+created_at: 2026-07-04
+updated_at: 2026-07-04
+review_reason: ""
+merge_history: []
+tags: ["php", "programming", "w3schools", "forms", "validation", "required"]
+raw_sources: ["https://www.w3schools.com/php/php_form_required.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[PHP Form Required]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+The pattern for making a field "required" is a mirrored if/else: `empty($_POST["field"])` sets an ERROR message and leaves the display variable untouched, while the else branch runs the field through `test_input()` — meaning error state and sanitized value live in two separate variables that are only ever set on opposite branches of the same check. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **`empty($_POST["field"])`** — checks if a field was left blank. [S1]
+- **Error variables** — `$nameErr`, `$emailErr`, `$genderErr`, `$websiteErr` — hold per-field error messages, initialized empty. [S1]
+- **Required vs. optional handling** — required fields set an error message when empty; optional fields just stay empty (no error) when blank. [S1]
+- **Displaying errors inline** — `<span class="error"><?php echo $nameErr;?></span>` placed next to each field. [S1]
+
+## 📖 세부 내용 (Details)
+- Required field check: `if (empty($_POST["name"])) { $nameErr = "Name is required"; } else { $name = test_input($_POST["name"]); }`. [S1]
+- Optional field (no error): `if (empty($_POST["website"])) { $website = ""; } else { $website = test_input($_POST["website"]); }`. [S1]
+- Inline error display: `Name: <input type="text" name="name"> <span class="error">* <?php echo $nameErr;?></span>`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 필수 필드(이름/이메일/성별)와 선택 필드(웹사이트/코멘트)를 다르게 처리하는 것이 실전 폼 검증의 표준 구조다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Required-field validation with error message (PHP):
+```php
+if (empty($_POST["name"])) {
+    $nameErr = "Name is required";
+} else {
+    $name = test_input($_POST["name"]);
+}
+```
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.89
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[PHP Tutorial]]
+- **관련 개념:** [[PHP Form Validation]], [[PHP Form URL Email]]
+- **참조 맥락:** 필수 필드 검증 — 이메일/URL 형식 검증(URL Email) 챕터로 이어짐.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — PHP Forms - Required Fields — https://www.w3schools.com/php/php_form_required.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "PHP Forms - Required Fields" page (Astra wiki-curation, P-Reinforce v3.1 format).