$file = new CURLFile('test.png', 'image/png', 'test.png');

$data = [
    'file' => $file,
    'burasi_diger_post_fieldleri' => '123456',
    'bir_tane_daha_ekleyeyim' => '58934'
];

$ch = curl_init('https://siteadresi.com/');  

curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: multipart/form-data']);

$response = curl_exec($ch);

print $response;
curl_close($ch);