(PHP 4, PHP 5, PHP 7)
imap_headers — Returns headers for all messages in a mailbox
$imap_stream
) : arrayReturns headers for all messages in a mailbox.
Returns an array of string formatted with header info. One element per mail message.
Just a helpful hint, many IMAP servers will include non-standard flags in curly braces before the subject in the response of this function. Pretty sure this is the only way to determine if a message has been forwarded, for example, when using the IMAP functions. The first flag (or more) may be prefixed with a dollar sign ($). It's (probably) likely that any such flags received by a server can be passed through imap_append to that server, as well.
Message flag descriptions can be found on official imap_headerinfo page (http://www.php.net/manual/en/function.imap-headerinfo.php) in "Return Value" paragraph.
Ok, this page is driving me crazy. Parsing the lines returned in the array is simple enough but there is no definitions on what the flags mean. So I searched the web to find the answer and this is what I was able to gather:
A - Answered: email has been replied to
N - New: Recent and not seen
R - Recent: Recent and seen
U - Unread: The message has not been read yet
F - Flagged: Message is "flagged" for urgent/special attention
D - Deleted: Message is "deleted" for removal by later EXPUNGE
X - Draft: Message has not completed composition (marked as a draft).
please correct me if I am wrong...
This function will not return a full subject line if it is longer than 25 characters. I found this out after trying to search each header and move the email to a different folder depending on what the subject was (searching for year and project number).