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title

PHP File Upload

🎯 한 줄 통찰 (One-line insight)

Checking a file's extension alone is NOT proof it's a real image — the tutorial uses getimagesize() specifically to detect "fake images" (files renamed with an image extension but containing different content), showing that upload validation needs content-based checks, not just filename-based ones. [S1]

🧠 핵심 개념 (Core concepts)

Required setup — file_uploads = On in php.ini; HTML form must have method="post" AND enctype="multipart/form-data". [S1]
$_FILES["fieldname"] — array holding uploaded file info: ["name"], ["tmp_name"], ["size"]. [S1]
getimagesize() — detects whether an uploaded file is a genuine image (vs. a renamed fake). [S1]
file_exists() — checks for filename collisions before saving. [S1]
pathinfo($file, PATHINFO_EXTENSION) — extracts the file extension for type-checking. [S1]
move_uploaded_file($tmp_name, $target) — the final step that actually relocates the uploaded file from its temporary location to the destination. [S1]
$uploadOk flag pattern — accumulates validation failures across multiple checks (file exists, size limit, file type) before deciding whether to actually move the file. [S1]

📖 세부 내용 (Details)

Form requirements: <form action="upload.php" method="post" enctype="multipart/form-data"> <input type="file" name="fileToUpload"> <input type="submit"> </form>. [S1]
Real-image check: $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]); if($check !== false) { $uploadOk = 1; } else { echo "File is not an image."; $uploadOk = 0; }. [S1]
Size limit (500KB): if ($_FILES["fileToUpload"]["size"] > 500000) { echo "Sorry, your file is too large."; $uploadOk = 0; }. [S1]
Type whitelist: if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif") { $uploadOk = 0; }. [S1]
Final move: if ($uploadOk == 0) { echo "Sorry, your file was not uploaded."; } else { if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) { echo "uploaded."; } }. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

확장자만으로는 불충분: getimagesize()로 실제 이미지 콘텐츠인지 확인해야 하며, 확장자 이름만으로는 가짜 이미지를 걸러낼 수 없다는 점이 강조됨. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 파일 존재 여부/크기/타입을 순차적으로 검사한 후 최종적으로 move_uploaded_file()로 이동하는 것이 안전한 업로드 처리의 표준 패턴이다. [S1]

💻 코드 패턴 (Code patterns)

Verifying the uploaded file is a genuine image (PHP):

if (isset($_POST["submit"])) {
    $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
    if ($check !== false) {
        echo "File is an image - " . $check["mime"] . ".";
    } else {
        echo "File is not an image.";
    }
}

✅ 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 Create, PHP Cookies, PHP Filter
참조 맥락: 파일 처리 섹션의 마지막 — 쿠키(Cookies) 섹션으로 이어짐.

📚 출처 (Sources)

[S1] W3Schools — PHP File Upload — https://www.w3schools.com/php/php_file_upload.asp

📝 변경 이력 (Change history)

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

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