string imap_fetchheader ( resource imap_stream, int msgno [, int options] )
This function causes a fetch of the complete, unfiltered
RFC2822
format header of the specified message as a text string and
returns that text string.
The options are:
FT_UID - The msgno
argument is a UID
FT_INTERNAL - The return string
is in "internal" format, without any attempt to
canonicalize to CRLF newlines
FT_PREFETCHTEXT - The RFC822.TEXT
should be pre-fetched at the same time. This avoids an
extra RTT on an IMAP connection if a full message text is
desired (e.g. in a "save to local file" operation)