cURL PHP API调用不起作用

Trying to make a cURL PHP API call to WEocr, but I can't receive a response by the API. Here's the code I am using:

    $url = 'http://jimbocho.ocrgrid.org/cgi-bin/weocr/submit_ocrad.cgi';
    $header = array('Content-Type: multipart/form-data');
    $fields = array('userfile' => '@' . $_FILES['file']['tmp_name'][0]);
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
    $result = json_decode(curl_exec($ch));

I don't know if i'm writing a incorrect syntax of the cURL command.

Thanks in advance.

The error i'm getting:

Sorry!
Received a null image (0byte). See TIPS page. 

I guess your path isn't correct, try this:

$url = 'http://jimbocho.ocrgrid.org/cgi-bin/weocr/submit_ocrad.cgi';
$file_name_with_full_path = '/home/example/dir/sample.jpeg';
$post = array('userfile'=>'@'.$file_name_with_full_path);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
$result=curl_exec ($ch);
curl_close ($ch);

Update based on your comments, also try this:

$file_new = /path/to/your/file.jpg
$cmd="curl -F userfile=$file_new \ 
      -F outputencoding=\"utf-8\" \
      F outputformat=\"txt\" \ 
      http://maggie.ocrgrid.org/cgi-bin/weocr/ocr_scene.cgi >result.txt"
$result = shell_exec($cmd);
print_r($result);

Note: You don't need to set CURLOPT_POST 1 if you're using CURLOPT_POSTFIELDS , curl do that for you automagically. Curl also sets the Content-Type: multipart/form-data, if the post content is an array, that's your case, no need for that too.

CURLOPT_POSTFIELDS

The full data to post in a HTTP "POST" operation. To post a file, prepend a filename with @ and use the full path. The filetype can be explicitly specified by following the filename with the type in the format ';type=mimetype'. This parameter can either be passed as a urlencoded string like 'para1=val1&para2=val2&...' or as an array with the field name as key and field data as value. If value is an array, the Content-Type header will be set to multipart/form-data. As of PHP 5.2.0, value must be an array if files are passed to this option with the @ prefix. As of PHP 5.5.0, the @ prefix is deprecated and files can be sent using CURLFile. The @ prefix can be disabled for safe passing of values beginning with @ by setting the CURLOPT_SAFE_UPLOAD option to TRUE.