Here's how to upload a file to a server using PHP cURL. It took me a little longer than planned to sort this one out, as the API I was communicating with required the top level key in the post data array to be 'file'. See my note below.

// Helper function courtesy of
function getCurlValue($filename, $contentType, $postname)
    // PHP 5.5 introduced a CurlFile object that deprecates the old @filename syntax
    // See:
    if (function_exists('curl_file_create')) {
        return curl_file_create($filename, $contentType, $postname);
    // Use the old style if using an older version of PHP
    $value = "@{$filename};filename=" . $postname;
    if ($contentType) {
        $value .= ';type=' . $contentType;
    return $value;
$filename = '/path/to/file.jpg';
$cfile = getCurlValue($filename,'image/jpeg','cattle-01.jpg');
//NOTE: The top level key in the array is important, as some apis will insist that it is 'file'.
$data = array('file' => $cfile);
$ch = curl_init();
$options = array(CURLOPT_URL => 'http://your/server/api/upload',
             CURLOPT_RETURNTRANSFER => true,
             CURLINFO_HEADER_OUT => true, //Request header
             CURLOPT_HEADER => true, //Return header
             CURLOPT_SSL_VERIFYPEER => false, //Don't veryify server certificate
             CURLOPT_POST => true,
             CURLOPT_POSTFIELDS => $data
curl_setopt_array($ch, $options);
$result = curl_exec($ch);
$header_info = curl_getinfo($ch,CURLINFO_HEADER_OUT);
$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$header = substr($result, 0, $header_size);
$body = substr($result, $header_size);
<!doctype html>
    <meta charset="utf-8">
    <title>File Upload results</title>
    <p>Raw Result: <?=$result?>
    <p>Header Sent: <?=$header_info?></p>
    <p>Header Received: <?=$header?></p>
    <p>Body: <?=$body?></p>
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