(PHP 5 >= 5.1.3, PHP 7)
imap_savebody — Save a specific body section to a file
$imap_stream
   , mixed $file
   , int $msg_number
   [, string $part_number = ""
   [, int $options = 0
  ]] ) : boolSaves a part or the whole body of the specified message.
imap_stream由 imap_open() 返回的 IMAP 流。
fileThe path to the saved file as a string, or a valid file descriptor returned by fopen().
msg_numberThe message number
part_numberThe part number. It is a string of integers delimited by period which index into a body part list as per the IMAP4 specification
optionsA bitmask with one or more of the following:
FT_UID - The msg_number is a UID
         
        FT_PEEK - Do not set the \Seen flag if
          not already set
         
        FT_INTERNAL - The return string is in
          internal format, will not canonicalize to CRLF.
         
        
   成功时返回 TRUE, 或者在失败时返回 FALSE。