Marks messages listed in msg_number for deletion.
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.
imap_streamAn IMAP stream returned by imap_open().
msg_numberThe message number
options
You can set the FT_UID which tells the function
to treat the msg_number argument as an
UID.
注意: 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.