webDAV/CalDAV client class experience ?

Hello, I'm working on this one for more than a year (personal project) - but I'm turning pretty desperate here. I'm trying to connect to 2 Calendars through the CalDAV protocol. The calendars are hosted by 2 webmail providers. If I try to sync through a dedicated calendar, like iCal or Thunderbird Lightning add-on, this works fine. However, once I try to do it through "native" PHP, I fail miserably - even if I mimick HTTP requests as recorded by Charles (HTTP debugging proxy). Up until now, I used the inc_caldav-client-v2.php, which worked for a while and then stopped all of a sudden. The PUT requests failed, and then any HTTP request got caught in what appears to be a socket timeout. My question: is anyone using some webDAV/CalDAV class that actually works ? If not, any tutorial on the subject is also deeply appreciated ( all I can rely on is the IETF spec rfc4791, which is far from accesible reading material)