Returns TRUE.
imap_delete() marks messages
listed in msg_number for
deletion. The optional
flags parameter only has a single option, FT_UID, which tells the function to
treat the msg_number
argument as a UID. Messages
marked for deletion will stay in the mailbox until either
imap_expunge() is called or
imap_close() is called with the optional parameter
CL_EXPUNGE.
注: POP3 mailboxes do not have their message flags saved between connections, so imap_expunge() must be called during the same connection in order for messages marked for deletion to actually be purged.