2nd/10_Wiki/Dev/Topic_PHP/PHP_Looping_Foreach.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
php-looping-foreach	PHP Looping Foreach	Programming_Language	draft	conceptual		foreach loop byref PHP foreach 반복문		B	0.9	2026-07-04	2026-07-04			php programming w3schools loops foreach arrays	https://www.w3schools.com/php/php_looping_foreach.asp

PHP Looping Foreach

🎯 한 줄 통찰 (One-line insight)

By default, modifying the loop variable inside foreach does NOT affect the original array — but adding a single & (foreach ($colors as &$x)) switches to by-reference assignment, meaning changes to $x inside the loop DO mutate $colors directly, a one-character difference with a completely different mutation contract. [S1]

🧠 핵심 개념 (Core concepts)

• foreach ($array as $value) — loops over indexed array values. [S1]
• foreach ($array as $key => $value) — loops over associative arrays, exposing both key and value. [S1]
• Works on objects too — iterates over public properties ($name => $value). [S1]
• By-value default — modifying the loop variable does not change the source array. [S1]
• By-reference (&$x) — modifying the loop variable DOES change the source array. [S1]
• break / continue — same semantics as other loops. [S1]
• Alternative syntax — foreach (...) : ... endforeach;. [S1]

📖 세부 내용 (Details)

• Indexed array: $colors = array("red", "green", "blue", "yellow"); foreach ($colors as $value) { echo "$value <br>"; }. [S1]
• Associative array: $members = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43"); foreach ($members as $key => $value) { echo "$key : $value <br>"; }. [S1]
• Object properties: foreach ($myCar as $x => $y) { echo "$x: $y <br>"; }. [S1]
• By-value (no mutation): foreach ($colors as $x) { if ($x == "blue") $x = "pink"; } // $colors unchanged. [S1]
• By-reference (mutates original): foreach ($colors as &$x) { if ($x == "blue") $x = "pink"; } // $colors now has "pink" instead of "blue". [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 참조 전달의 예외적 동작: 기본적으로 반복 변수 수정은 원본 배열에 영향을 주지 않지만, &를 붙이면 원본이 실제로 변경된다는 점이 두 예제로 명확히 대비됨. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 배열 값을 순회하며 특정 조건에 따라 원본을 직접 수정해야 할 때 &$x 참조 전달이 사용된다. [S1]

💻 코드 패턴 (Code patterns)

By-reference foreach mutates the original array (PHP):

$colors = array("red", "green", "blue", "yellow");
foreach ($colors as &$x) {
    if ($x == "blue") $x = "pink";
}
var_dump($colors); // "blue" is now "pink" in the original array

✅ 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 Looping For, PHP Arrays, PHP OOP Classes Objects
• 참조 맥락: 배열/객체 순회 전용 반복문 — break/continue 챕터로 이어짐.

📚 출처 (Sources)

• [S1] W3Schools — PHP foreach Loop — https://www.w3schools.com/php/php_looping_foreach.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "PHP foreach Loop" page (Astra wiki-curation, P-Reinforce v3.1 format).