---
id: php-string-modify
title: "PHP String Modify"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["strtoupper", "str_replace", "explode", "PHP 문자열 변형"]
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", "modify"]
raw_sources: ["https://www.w3schools.com/php/php_string_modify.asp"]
applied_in: []
github_commit: ""
---

# [[PHP String Modify]]

## 🎯 한 줄 통찰 (One-line insight)
`explode()`'s separator parameter is REQUIRED, not optional — unlike some split functions in other languages that default to whitespace, PHP's `explode()` always demands you specify exactly what to split on, making the split behavior fully explicit every time. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`strtoupper()` / `strtolower()`** — case conversion. [S1]
- **`str_replace(search, replace, subject)`** — substring replacement. [S1]
- **`strrev()`** — reverses a string. [S1]
- **`trim()`** — removes leading/trailing whitespace. [S1]
- **`explode(separator, string)`** — splits a string into an array by a required separator. [S1]
- **`print_r()`** — displays array contents in a readable format. [S1]

## 📖 세부 내용 (Details)
- Case conversion: `strtoupper($x); strtolower($x);`. [S1]
- Replace: `echo str_replace("World", "Dolly", $x); // "Hello Dolly!"`. [S1]
- Reverse: `echo strrev($x);`. [S1]
- Trim: `$x = " Hello World! "; echo trim($x);`. [S1]
- Explode with required separator: `$x = "Hello lovely World!"; $y = explode(" ", $x); print_r($y); // ["Hello", "lovely", "World!"]`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **explode() 구분자 필수**: 분리자를 생략할 수 없고 반드시 지정해야 한다는 점이 명시됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 공백 기준으로 문장을 단어 배열로 나누는 explode()가 텍스트 처리의 표준 패턴이다. [S1]

## 💻 코드 패턴 (Code patterns)
Splitting a string into an array with explode() (PHP):
```php
$x = "Hello lovely World!";
$y = explode(" ", $x);
print_r($y); // Array ( [0] => Hello [1] => lovely [2] => World! )
```

## ✅ 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 Arrays]], [[PHP String Concatenate]]
- **참조 맥락:** 문자열 변형 함수 — explode()는 배열(Arrays) 챕터와 직접 연결됨.

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

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