... mixed dio_fcntl ( resource fd, int cmd [, mixed arg]) . ... Some commands require additional arguments args to be supplied. arg is an associative array, when cmd is F_SETLK or F_SETLLW, with the following keys: . ... If the lock is held by someone else dio_fcntl() returns -1. F_SETLKW - like F_SETLK, but in case the lock is held by someone else, dio_fcntl() waits until the lock is released. F_GETLK - dio_fcntl() returns an associative array (as described above) if someone else prevents lock. ...