---
id: php-syntax
title: "PHP Syntax"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["PHP 기본 문법"]
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", "syntax"]
raw_sources: ["https://www.w3schools.com/php/php_syntax.asp"]
applied_in: []
github_commit: ""
---

# [[PHP Syntax]]

## 🎯 한 줄 통찰 (One-line insight)
PHP's case-sensitivity is asymmetric — keywords/functions/classes are case-INsensitive (`ECHO` works same as `echo`), but variable names are strictly case-SENSITIVE (`$color` and `$COLOR` are two completely different variables), a distinction the source demonstrates directly by showing the second echo silently printing nothing meaningful. [S1]

## 🧠 핵심 개념 (Core concepts)
- **PHP tags** — a script starts with `<?php` and ends with `?>`. [S1]
- **`.php` extension** — default file extension; files mix HTML and PHP code freely. [S1]
- **Semicolons required** — all PHP statements end with `;`. [S1]
- **Case-insensitive**: keywords, function names, class names, user-defined functions. [S1]
- **Case-sensitive**: variable names. [S1]

## 📖 세부 내용 (Details)
- Basic script structure: `<?php echo 'Hello World!'; ?>` embedded inside HTML. [S1]
- Keyword case-insensitivity: `ECHO 'Hello World!<br>'; echo 'Hello World!<br>';` — both legal and equivalent. [S1]
- Variable case-sensitivity: `$color = "red"; echo "My car is $color<br>"; echo "My house is $COLOR";` — `$COLOR` is undefined/different from `$color`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **대소문자 구분의 비대칭성**: 키워드/함수/클래스는 대소문자 구분 없음, 하지만 변수명은 대소문자 구분됨이 명시적으로 대비됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — HTML과 PHP 코드를 한 파일에서 혼합하는 것이 PHP 스크립트의 기본 작성 방식이다. [S1]

## 💻 코드 패턴 (Code patterns)
Variable name case-sensitivity trap (PHP):
```php
<?php
$color = "red";
echo "My car is $color<br>";   // red
echo "My house is $COLOR";     // undefined — $COLOR != $color
?>
```

## ✅ 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 Install]], [[PHP Comments]], [[PHP Variables]]
- **참조 맥락:** PHP 기본 문법 — 주석(Comments), 변수(Variables) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — PHP Syntax — https://www.w3schools.com/php/php_syntax.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "PHP Syntax" page (Astra wiki-curation, P-Reinforce v3.1 format).