php-cgi: cgi_main.c => max_requests = 500?

Hi all, I am new to PHP and to this forum. I was testing my webserver with PHP and found out that after 500 requests the php-cgi process finished (without cores). I ran it with valgrind and no memory leaks :). I thought it couldn't be a coincidence that, always, after 500 requests, php-cgi finished; so I have had a look at cgi_main.c and found: max_requests = 500; I have seen that the environment variable: PHP_FCGI_MAX_REQUESTS might be used to override this value; why php-cgi has to finish after n requests? Thanks in advance, Guido.