PHP - CURLFile什么都不显示

Question

I'm using Codeigniter and trying to send a file to another server but when I use new CURLFile() to make a file, the screen is display nothing and the file isn't sent.

Here's my code :

Testing.php

public function sendFile(){
    $ch = curl_init();

    $cfile = new CURLFile(base_url().'assets/upload/RAD PAPER.doc');
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, array('file' => $cfile, 'filename'=>'name'));
    curl_setopt($ch, CURLOPT_URL, 'http://localhost/devel/api/receive');
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: multipart/form-data'));
    curl_setopt($ch, CURLOPT_HEADER, 1);
    curl_setopt($ch, CURLINFO_HEADER_OUT, true);
    curl_exec($ch);
    curl_close($ch);
}

and in the other server :

Api.php

public function receive(){
    $folder = base_url().'assets/';
    $path = $folder . $_FILES['file']['name']; 
    if(move_uploaded_file($_FILES['file']['tmp_name'], $path)) {
        echo "The file ".  basename( $_FILES['file']['name']). " has been uploaded";
    } 
    echo "smthg to print";
    print_r($_FILES['file']);
}

It's looks like function receive is never be called. But when I change this line :

curl_setopt($ch, CURLOPT_POSTFIELDS, array('file' => $cfile, 'filename'=>'name'));

to :

curl_setopt($ch, CURLOPT_POSTFIELDS, array('file' => 'thisisstring', 'filename'=>'name'));

return me the message 'smthg to print' in Api.php but $_FILES['file'] is undefined because it's not a file. What's wrong with my code? Do I wrong in using CURLFile? I'd try curl_file_create() too.