Note that DateTimeZone::listIdentifiers(DateTimeZone::AUSTRALIA) contains a subset of the timezones listed on this page. Some of the timezones listed are kept for backwards compatibility only.
Australian Timezones with DateTimeZone::AUSTRALIA
Australia/Adelaide
Australia/Brisbane
Australia/Broken_Hill
Australia/Currie
Australia/Darwin
Australia/Eucla
Australia/Hobart
Australia/Lindeman
Australia/Lord_Howe
Australia/Melbourne
Australia/Perth
Australia/Sydney
Australian Timezones with DateTimeZone::ALL_WITH_BC
Australia/ACT
Australia/Adelaide
Australia/Brisbane
Australia/Broken_Hill
Australia/Canberra
Australia/Currie
Australia/Darwin
Australia/Eucla
Australia/Hobart
Australia/LHI
Australia/Lindeman
Australia/Lord_Howe
Australia/Melbourne
Australia/NSW
Australia/North
Australia/Perth
Australia/Queensland
Australia/South
Australia/Sydney
Australia/Tasmania
Australia/Victoria
Australia/West
Australia/Yancowinna
I could not find documentation to list when certain timezones were deprecated, but any timezone that only appears in the second list is for backward compatibility purposes only and could be removed in a future release of PHP.