function curlfile($url, $url2){

   $ch = curl_init();
   curl_setopt($ch, CURLOPT_URL, $url);
   curl_setopt($ch, CURLOPT_HEADER, 1);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
   curl_setopt($ch, CURLOPT_POST, true);
   curl_setopt($ch, CURLOPT_POSTFIELDS, 'username=логинpassword=пассlogin=submit');
   curl_setopt($ch, CURLOPT_URL, $url2);
   $data = curl_exec($ch);
   #if(preg_match('#Location: ([S]+)#',$data,$rr)){$preg = $rr[1];} else {die('error c1');}
   curl_close($ch);
   return $data;
}

var_dump(curlfile('https://dxp.ru/takelogin.php', 'https://dxp.ru/index.php'));