PHP의 파일 업로드 및 다운로드 기술

<form action="upload.php" method="post" enctype="multipart/form-data">
  <input type="file" name="fileToUpload" id="fileToUpload">
  <input type="submit" value="上传文件" name="submit">
</form>

<?php
$target_dir = "./uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

// 检查文件是否是图片
if(isset($_POST["submit"])) {
  $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
  if($check !== false) {
    echo "File is an image - " . $check["mime"] . ".";
    $uploadOk = 1;
  } else {
    echo "File is not an image.";
    $uploadOk = 0;
  }
}

// 检查文件是否已经存在
if (file_exists($target_file)) {
  echo "Sorry, file already exists.";
  $uploadOk = 0;
}

// 检查文件大小
if ($_FILES["fileToUpload"]["size"] > 500000) {
  echo "Sorry, your file is too large.";
  $uploadOk = 0;
}

// 允许上传的文件类型
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
}

// 如果所有检查都通过，上传文件
if ($uploadOk == 0) {
  echo "Sorry, your file was not uploaded.";
} else {
  if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
    echo "The file ". htmlspecialchars( basename( $_FILES["fileToUpload"]["name"])). " has been uploaded.";
  } else {
    echo "Sorry, there was an error uploading your file.";
  }
}
?>

$file = "./downloads/test.txt";

// 设置HTTP头信息以告诉浏览器下载文件
header("Content-disposition: attachment;filename=".basename($file));
header("Content-type: application/octet-stream");
header("Content-Length: ".filesize($file));
header("Pragma: no-cache");
header("Expires: 0");

// 将文件内容读取并输出给浏览器
readfile($file);

$content = "Hello, world!";
$filename = "test.txt";
$file = "./downloads/".$filename;

// 将内容写入到文件中
$handle = fopen($file, "w");
fwrite($handle, $content);
fclose($handle);

// 返回下载文件给客户端
header("Content-disposition: attachment;filename=".$filename);
header("Content-type: application/octet-stream");
header("Content-Length: ".filesize($file));
header("Pragma: no-cache");
header("Expires: 0");
readfile($file);

// 下载完成后删除服务器端的文件
unlink($file);