Curl загрузка файла не зная расширения

Использую curl Не понимаю, как сохранять файл не зная его расширения?! Т.к. могут быть варианты:zip/xml/xls и тд. Пробовал $info = curl_getinfo($ch); получил это:

    Array
(
    [url] => https://*****путь****
    [content_type] => application/vnd.ms-excel
    [http_code] => 200
    [header_size] => 837
    [request_size] => 161
    [filetime] => -1
    [ssl_verify_result] => 0
    [redirect_count] => 0
    [total_time] => 6.440045
    [namelookup_time] => 1.8E-5
    [connect_time] => 1.8E-5
    [pretransfer_time] => 9.5E-5
    [size_upload] => 0
    [size_download] => 705024
    [speed_download] => 109475
    [speed_upload] => 0
    [download_content_length] => -1
    [upload_content_length] => 0
    [starttransfer_time] => 6.354781
    [redirect_time] => 0
    [redirect_url] => 
    [primary_ip] => xx.xxx.xxx.xxx
    [certinfo] => Array
        (
        )
    [primary_port] => 443
    [local_ip] => 192.168.1.220
    [local_port] => 40374
)
Array
(
    [url] => ftp://**путь***.xml
    [content_type] => 
    [http_code] => 226
    [header_size] => 0
    [request_size] => 0
    [filetime] => -1
    [ssl_verify_result] => 0
    [redirect_count] => 0
    [total_time] => 2.175119
    [namelookup_time] => 1.7E-5
    [connect_time] => 1.7E-5
    [pretransfer_time] => 0.023471
    [size_upload] => 0
    [size_download] => 24336367
    [speed_download] => 11188522
    [speed_upload] => 0
    [download_content_length] => 24336367
    [upload_content_length] => 0
    [starttransfer_time] => 0.023491
    [redirect_time] => 0
    [redirect_url] => 
    [primary_ip] => xx.xx.xx.xx
    [certinfo] => Array
        (
        )
    [primary_port] => 28996
    [local_ip] => 192.168.1.220
    [local_port] => 41852
)

если в первом случае хоть что то понятно

[content_type] => application/vnd.ms-excel

то во втором пусто, хотя явно загружаю xml