(PHP 3 >= 3.0.3, PHP 4, PHP 5)
imap_uid -- This function returns the UID for the given message sequence numberThis function returns the UID for the given message sequence number. An UID is a unique identifier that will not change over time while a message sequence number may change whenever the content of the mailbox changes. This function is the inverse of imap_msgno().
Note: This is not supported by POP3 mailboxes.
See also: imap_msgno().