废话少说，直接上代码：

<?php
/**
 * Note:for octet-stream upload
 * 这个是流式上传PHP文件
 * Please be amended accordingly based on the actual situation
 */
$post_input = "php://input";
$save_path = dirname(__FILE__);
$postdata = file_get_contents($post_input);
if (isset($postdata) && strlen($postdata) > 0) {
 $filename = $save_path . "/" . uniqid() . ".jpg";
 $handle = fopen($filename, "w+");
 fwrite($handle, $postdata);
 fclose($handle);
 if (is_file($filename)) {
  echo "Image data save successed,file:" . $filename;
  exit ();
 } else {
  die ("Image upload error!");
 }
} else {
 die ("Image data not detected!");
}

<?php
/**
 * Note:for multipart/form-data upload
 * 这个是标准表单上传PHP文件
 * Please be amended accordingly based on the actual situation
 */
if (!$_FILES["Filedata"]) {
 die ("Image data not detected!");
}
if ($_FILES["Filedata"]["error"] > 0) {
 switch ($_FILES ["Filedata"] ["error"]) {
  case 1 :
   $error_log = "The file is bigger than this PHP installation allows";
   break;
  case 2 :
   $error_log = "The file is bigger than this form allows";
   break;
  case 3 :
   $error_log = "Only part of the file was uploaded";
   break;
  case 4 :
   $error_log = "No file was uploaded";
   break;
  default :
   break;
 }
 die ("upload error:" . $error_log);
} else {
 $img_data = $_FILES["Filedata"]["tmp_name"];
 $size = getimagesize($img_data);
 $file_type = $size["mime"];
 if (!in_array($file_type, array("image/jpg", "image/jpeg", "image/pjpeg", "image/png", "image/gif"))) {
  $error_log = "only allow jpg,png,gif";
  die ("upload error:" . $error_log);
 }
 switch ($file_type) {
  case "image/jpg" :
  case "image/jpeg" :
  case "image/pjpeg" :
   $extension = "jpg";
   break;
  case "image/png" :
   $extension = "png";
   break;
  case "image/gif" :
   $extension = "gif";
   break;
 }
}

if (!is_file($img_data)) {
 die ("Image upload error!");
}

// 图片保存路径,默认保存在该代码所在目录(可根据实际需求修改保存路径)
$save_path = dirname(__FILE__);
$uinqid = uniqid();
$filename = $save_path . "/" . $uinqid . "." . $extension;
$result = move_uploaded_file($img_data, $filename);
if (!$result || !is_file($filename)) {
 die ("Image upload error!");
}
echo "Image data save successed,file:" . $filename;
exit ();

备注：美图秀秀提供两个上传接口供测试
一个是octet-stream方式上传，地址为：http://imgkaka.meitu.com/xiuxiu_web_pic_save.php
另一个是multipart/form-data方式上传，地址为：http://web.upload.meitu.com/image_upload.php
表单名称为"upload_file"。