Read the list of mailboxes, takes a string to search for in the text of the mailbox ()
array imap_listscan ( resource imap_stream, string ref, string pattern, string content )

Returns an array containing the names of the mailboxes that have content in the text of the mailbox.

This function is similar to imap_listmailbox(), but it will additionally check for the presence of the string content inside the mailbox data.

See imap_getmailboxes() for a description of ref and pattern.