is_color_hex() validates hex color strings
(#RGB, #RGBA, #RRGGBB,
#RRGGBBAA).is_ipv6() validates IPv6 address strings, including
compressed (::) and IPv4-embedded forms (#18).is_iso_date() and is_iso_datetime()
validate ISO 8601 date and datetime strings.is_mime() validates MIME type strings against the
IANA-registered top-level types.