// set message as seen
$imap->setMessageSeen('inbox', 175, true);
// set message as unseen
$imap->setMessageSeen('inbox', 175, false);
// set message as flagged
$imap->setMessageFlagged('inbox', 175, true);
// set message as unflagged
$imap->setMessageFlagged('inbox', 175, false);
// set message as answered
$imap->setMessageAnswered('inbox', 175, true);
// set message as unanswered
$imap->setMessageAnswered('inbox', 175, false);
// mark group of messages as seen
$imap->setMessageSeen('inbox', 171, true, true);
$imap->setMessageSeen('inbox', 172, true, true);
$imap->setMessageSeen('inbox', 173, true, true);
// and saves it
$imap->expunge();
// delete message
$imap->deleteMessage('inbox', 174);
// mark group of messages as deleted
$imap->deleteMessage('inbox', 175, true);
$imap->deleteMessage('inbox', 176, true);
$imap->deleteMessage('inbox', 177, true);
// and delete it
$imap->expunge();
// disconnect from server
$imap->disconnect();
} catch (Exception $imapEx) {
print_r($imapEx);
}