I handled this problem by using "shot and forget" requests. that's when you call a php-script using a http request, but you don't read the answer of the server, but close the stream right after the request. Additionally the close-connection tag in the header of the request must be "close", if I recall correctly.
Of course this only works when you don't have to read the servers answer.
Of course this only works when you don't have to read the servers answer.