(PHP 4, PHP 5, PHP 7, PHP 8)
imap_fetchheader — Returns header for a message
$imap, int $message_num, int $flags = 0): string|falseThis function causes a fetch of the complete, unfiltered » RFC2822 format header of the specified message.
imapAn IMAP\Connection instance.
message_numThe message number
flags
       The possible flags are:
       
FT_UID - The message_num
          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)
         
        
   Returns the header of the specified message as a text string,  或者在失败时返回 false.
  
| 版本 | 说明 | 
|---|---|
| 8.1.0 | The imapparameter expects an IMAP\Connection
  instance now; previously, a 资源(resource) was expected. |