2nd/10_Wiki/Dev/Topic_PHP/PHP_Numbers.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-numbers	PHP Numbers	Programming_Language	draft	conceptual		is_int is_float NAN PHP 숫자		B	0.9	2026-07-04	2026-07-04			php programming w3schools numbers	https://www.w3schools.com/php/php_numbers.asp

PHP Numbers

🎯 한 줄 통찰 (One-line insight)

4 * 2.5 results in a FLOAT (10.0), not an integer, even though the mathematical result is a whole number — PHP's rule is that if ANY operand in an arithmetic expression is a float, the result is always stored as float, regardless of whether the value happens to be whole. [S1]

🧠 핵심 개념 (Core concepts)

• Three numeric types — Integer, Float, Numeric Strings; plus Infinity and NaN as special number-related values. [S1]
• is_int() / is_float() — type checks. [S1]
• Integer range — platform-dependent (32-bit: ±2,147,483,647; 64-bit: much larger); overflow silently becomes a float. [S1]
• Integer notations — decimal, hex (0x), octal (0), binary (0b). [S1]
• PHP_INT_MAX / PHP_INT_MIN / PHP_INT_SIZE — predefined integer limit constants. [S1]
• PHP_FLOAT_MAX / MIN / DIG / EPSILON (PHP 7.2+) — predefined float precision constants. [S1]
• is_finite() / is_infinite() — range checks against platform float limits. [S1]
• NAN ("Not A Number") — returned by invalid math operations; checked via is_nan(). [S1]
• is_numeric() — true for both actual numbers AND numeric strings (e.g., "5985"). [S1]
• intval() — extracts the integer value from a float or numeric-leading string. [S1]

📖 세부 내용 (Details)

• Float contagion rule: 4 * 2.5 is 10, but stored as float because one operand (2.5) is a float. [S1]
• Invalid math yields NAN: $x = acos(8); var_dump($x); var_dump(is_nan($x)); // true. [S1]
• Numeric string check: $x = "59.85" + 100; var_dump(is_numeric($x)); // true (arithmetic result). [S1]
• intval on string: $x = "23465.768"; echo intval($x); // 23465. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 부동소수점 전염 규칙: 연산 결과가 정수 값이어도 피연산자 중 하나가 float이면 결과 타입은 항상 float이 된다는 점이 명시적으로 강조됨. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — is_numeric()으로 사용자 입력이 숫자 형태인지 검증하는 것이 폼 처리의 실전 패턴이다. [S1]

💻 코드 패턴 (Code patterns)

Float contagion in arithmetic (PHP):

$result = 4 * 2.5;
var_dump($result); // float(10) — not int, because 2.5 is a float

✅ 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 Data Types, PHP Casting, PHP Math
• 참조 맥락: 숫자 타입의 세부 규칙 — 캐스팅(Casting)/수학함수(Math) 챕터로 이어짐.

📚 출처 (Sources)

• [S1] W3Schools — PHP Numbers — https://www.w3schools.com/php/php_numbers.asp

📝 변경 이력 (Change history)

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