使用纯Javascript和PHP上传文件

<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>

var fileInput = document.getElementById('fileToUpload');
var file = fileInput.files[0];
var reader = new FileReader();

reader.onload = function(e) {
  var preview = document.getElementById('preview');
  preview.src = e.target.result;
}

reader.readAsDataURL(file);

$targetDir = "uploads/";
$targetFile = $targetDir . basename($_FILES["fileToUpload"]["name"]);

if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $targetFile)) {
  echo "文件上传成功";
} else {
  echo "文件上传失败";
}