Description
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)