damn milter api:

"Furthermore, since there is not a one-to-one correspondence between
 threads and connections (N connections mapped onto M threads,
 M <= N), connection-specific data must be accessed through the handles
 provided by the Milter library."

which in other words means php_request_startup() and the corresponding
php_request_shutdown() will never be called for the same thread

sapi/milter/TODO

@@ -1,3 +1,4 @@
+extensions aren't loaded
 stdout to syslog
 testing
 documentation