(PHP 3 >= 3.0.3, PHP 4, PHP 5)
imap_uid -- 
     This function returns the UID for the given message sequence
     number
    
Description
int 
imap_uid ( resource imap_stream, int msgno )
     This 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().