---
id: php-strings
title: "PHP Strings"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["single vs double quotes", "PHP 문자열"]
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", "strings", "quotes"]
raw_sources: ["https://www.w3schools.com/php/php_string.asp"]
applied_in: []
github_commit: ""
---

# [[PHP Strings]]

## 🎯 한 줄 통찰 (One-line insight)
Double and single quotes are NOT interchangeable in PHP — double quotes interpolate variables and support rich escape sequences (`\n`, `\t`) at a slight performance cost, while single quotes output everything literally (even `$x` prints as `$x`, not its value) and only support `\'`/`\\`, making single quotes both faster and safer for constant strings with no variables. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Double quotes** — substitute variable values; support many escape sequences (`\n`, `\r`, `\t`, `\$`, `\"`). [S1]
- **Single quotes** — output text literally, including `$var` syntax as-is; only `\'` and `\\` are recognized escapes. [S1]
- **Performance** — single quotes are slightly faster (no parsing needed for variables/escapes). [S1]
- **Readability trade-off** — double quotes avoid concatenation clutter when many variables are embedded; single quotes are cleaner for constant strings. [S1]

## 📖 세부 내용 (Details)
- Variable substitution (double): `$x = "John"; echo "Hello $x"; // Hello John`. [S1]
- No substitution (single): `$x = "John"; echo 'Hello $x'; // Hello $x`. [S1]
- Escape sequence comparison: `echo "Hello $x\n"; echo "\tHow are you?\n";` (double, both work) vs. `echo 'Hello $x\n'; echo '\tHow are you?\n';` (single, literal output including the backslash sequences). [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **작은따옴표의 리터럴 출력**: $x 같은 변수 구문조차 작은따옴표 안에서는 값으로 치환되지 않고 문자 그대로 출력된다는 점이 예제로 명확히 검증됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 변수가 많은 문자열에는 큰따옴표, 상수 문자열에는 작은따옴표를 쓰는 것이 실전 코드 스타일의 일반적 관행이다. [S1]

## 💻 코드 패턴 (Code patterns)
Single quotes output variables literally (PHP):
```php
$x = "John";
echo "Hello $x";  // Hello John (double quotes interpolate)
echo 'Hello $x';  // Hello $x  (single quotes do not)
```

## ✅ 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 String Functions]], [[PHP String Concatenate]], [[PHP String Escape]]
- **참조 맥락:** 문자열 기초(따옴표 차이) — 문자열 함수 챕터로 이어짐.

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

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