---
id: php-cookies
title: "PHP Cookies"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["setcookie()", "$_COOKIE", "PHP 쿠키"]
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", "cookies"]
raw_sources: ["https://www.w3schools.com/php/php_cookies.asp"]
applied_in: []
github_commit: ""
---

# [[PHP Cookies]]

## 🎯 한 줄 통찰 (One-line insight)
`setcookie()` MUST run before any HTML output, including before the `<html>` tag — this is a hard requirement (not a style preference) because cookies are transmitted as part of the HTTP header, which must be sent before the response body; this is the same constraint sessions have. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Cookie** — a small text file the server stores in the browser, resent with every subsequent HTTP request. [S1]
- **`setcookie(name, value, expire, path, domain, secure, httponly)`** — only `name` is required; all others optional. [S1]
- **Must precede any output** — `setcookie()` must be called before `<html>` or any other output, since cookies are part of the HTTP header. [S1]
- **`$_COOKIE`** — superglobal for reading cookie values. [S1]
- **Deleting a cookie** — call `setcookie()` again with an expiration time in the PAST. [S1]
- **Auto URL-encoding** — cookie values are automatically URL-encoded on send and decoded on receipt (use `setrawcookie()` to opt out). [S1]

## 📖 세부 내용 (Details)
- Create + retrieve: `setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); ... if(isset($_COOKIE[$cookie_name])) { echo $_COOKIE[$cookie_name]; }`. [S1]
- Modify: re-calling `setcookie()` with a new value overwrites the old one. [S1]
- Delete: `setcookie("username", "", time() - 3600); // expiration in the past`. [S1]
- Check if cookies enabled: `setcookie("test_cookie", "test", time() + 3600, '/'); ... if(count($_COOKIE) > 0) { echo "Cookies are enabled."; }`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **출력 전 호출 필수**: setcookie()는 HTTP 헤더의 일부이므로 반드시 <html> 태그를 포함한 어떤 출력보다도 먼저 호출되어야 한다는 점이 두 번 강조됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 30일 만료 쿠키로 사용자 이름을 저장하는 것이 로그인 상태 유지의 대표 실전 사례다. [S1]

## 💻 코드 패턴 (Code patterns)
Creating and checking a cookie (PHP):
```php
<?php
$cookie_name = "username";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); // must run before <html>
?>
<html>
<body>
<?php
if (isset($_COOKIE[$cookie_name])) {
    echo "Value is: " . $_COOKIE[$cookie_name];
}
?>
</body>
</html>
```

## ✅ 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 File Upload]], [[PHP Sessions]], [[PHP Superglobals]]
- **참조 맥락:** 클라이언트 측 데이터 저장 — 세션(Sessions) 챕터로 직접 이어짐.

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

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