$filename = 'ox2.csv';
$ch = curl_init('
https://api-audience.yandex.ru/v1/management/segme...');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
'Authorization: OAuth ТУТ КЛЮЧ']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_HEADER, false);
$args['file'] = new CurlFile($filename, 'text/csv');
curl_setopt($ch, CURLOPT_POSTFIELDS, $args);
$curl_response = curl_exec($ch);
var_dump($curl_response);
$res = curl_exec($ch);
print_r($res);
curl_close($ch);
Разобрался сам.