[php] Posting raw image data as multipart/form-data in curl

I am trying to post an image with cURL in PHP using multipart/form-data header since API that I am sending to is expecting image to be sent as multi-part form.

I don't have problems talking to the API with other requests; only posting an image is an issue.

I am using this form on client side:

<form action="http://myServerURL" method="POST" enctype="multipart/form-data">
    <input type="file" name="file" />
    <input type="Submit">
</form>

and this is the server I am posting to (here I am trying to post this data forward to an API):

$ch = curl_init($url);
curl_setopt ($ch, CURLOPT_POST, 1);
curl_setopt ($ch, CURLOPT_POSTFIELDS, $imgRawData); // <-- raw data here hm?
curl_setopt( $ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt ($ch, CURLOPT_COOKIEFILE, $cookieJar);
curl_setopt( $ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLINFO_HEADER_OUT, 1); <-- using this as I wanted to check if HTTPHEADER is set
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: multipart/form-data')); <-- setting content-type header?
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1);

// i get response from the server
$response = curl_exec( $ch );

// with this I can check what kind of content type the last request had?
$requestContentType = curl_getinfo($ch,CURLINFO_CONTENT_TYPE);
echo "<br>request Content Type was:".$requestContentType."<br>";    

curl_close($ch);

echo "<br><b>SERVER POST IMAGE RESPONSE:</b><br>";
echo $response;

With the code below I am able to see my request headers:

curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLINFO_HEADER_OUT, true);

var_dump(curl_getinfo($ch));

The content-type in request-headers is shown correctly now. But it seems the image is not send correctly as API would expect. Unfortunately I don't have access to the API...

Any help appreciated, thank you

CURL OPERATION BETWEEN SERVER TO SERVER WITHOUT HTML FORM IN PHP USING MULTIPART/FORM-DATA

// files to upload

$filename = "https://example.s3.amazonaws.com/0.jpg";       

// URL to upload to (Destination server)

$url = "https://otherserver/image";

AND

    $curl = curl_init();

    curl_setopt_array($curl, array(
        CURLOPT_URL => $url,
        CURLOPT_RETURNTRANSFER => 1,
        CURLOPT_MAXREDIRS => 10,
        CURLOPT_TIMEOUT => 30,
        //CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
        CURLOPT_CUSTOMREQUEST => "POST",
        CURLOPT_POST => 1,
        CURLOPT_POSTFIELDS => file_get_contents($filename),
        CURLOPT_HTTPHEADER => array(
            //"Authorization: Bearer $TOKEN",
            "Content-Type: multipart/form-data",
            "Content-Length: " . strlen(file_get_contents($filename)),
            "API-Key: abcdefghi" //Optional if required
        ),
    ));

   $response = curl_exec($curl);

    $info = curl_getinfo($curl);
//echo "code: ${info['http_code']}";

//print_r($info['request_header']);

    var_dump($response);
    $err = curl_error($curl);

    echo "error";
    var_dump($err);
    curl_close($curl);

As of PHP 5.6 @$filePath will not work in CURLOPT_POSTFIELDS without CURLOPT_SAFE_UPLOAD being set and it is completely removed in PHP 7. You will need to use a CurlFile object, RFC here.

$fields = [
    'name' => new \CurlFile($filePath, 'image/png', 'filename.png')
];
curl_setopt($resource, CURLOPT_POSTFIELDS, $fields);