if you are echoing out the output and confused about the number...maybe this will help. i'm not totally sure it is accurate though.
ZIPARCHIVE::ER_EXISTS - 10
ZIPARCHIVE::ER_INCONS - 21
ZIPARCHIVE::ER_INVAL - 18
ZIPARCHIVE::ER_MEMORY - 14
ZIPARCHIVE::ER_NOENT - 9
ZIPARCHIVE::ER_NOZIP - 19
ZIPARCHIVE::ER_OPEN - 11
ZIPARCHIVE::ER_READ - 5
ZIPARCHIVE::ER_SEEK - 4