在使用multipart-formdata时，WebClient似乎不合适. 尝试使用HttpWebRequest-Class或将上载字段的名称更改为文件".
您可以通过在脚本的开头执行print_r(

As you are using multipart-formdata the WebClient seems to be unsuitable.
Either try to use the HttpWebRequest-Class or adapt the name of the upload-field to "file".
You can test the last one by do a print_r(

_FILES)来测试最后一个.

_FILES) at the beginning of the script.