It seems that for each snmpget() its own socket() will be opened. This is not closed after snmpget() finishes. Neither existing sockets are reused by subsequent snmpget() calls.
When querying a few switches with lots of ports the maximum file descriptor count of Apache is exhausted. Thus no more snmpget() are possible. Additionaly no more files can be read by this particular Apache process. Neither the PHP file, any include files nor any other files (like a .css file, ...).
This probably explains the observation of tkjode at phalnet dot com. Different to his case is that I'm using Linux.
