How to change the content type of the uploaded file in php?

I want to use the image upload API. It receives the image file via POST and sends me this URI of the image that I uploaded. but this API is sending me an error. If the content-to-content type is not a mime image type type (e.g. image / jpeg, image / png, ...)

But when I upload the image file via FTP and use CURL as the file upload, it sends me an error message because the Content-Type of this image is always an “application / octet stream”. I want to change this type of mime. Is there any way to change this?

Here is the code:

<?php
$fileUploadPostParams = Array(
    "uploadedfile" => "@/files.jpg"
);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://uix.kr/widget/parameter.php");
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fileUploadPostParams);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
echo curl_exec($ch);
?>

and here is the result:

...
===== file ===== 
Array
(
    [uploadedfile] => Array
        (
            [name] => 2312.jpg
            [type] => application/octet-stream
            ^^^^ I want to change here...
            [tmp_name] => /tmp/php5bigGV
            [error] => 0
            [size] => 383441
        )
)

sorry for bad english .. thanks