Description
array 
imap_sort ( resource stream, int criteria, int reverse [, int options [, string search_criteria]])
     Returns an array of message numbers sorted by the given
     parameters.
    
     Reverse is 1 for reverse-sorting.
    
     Criteria can be one (and only one) of the following:
     
        SORTDATE - message Date
       
        SORTARRIVAL - arrival date        
       
        SORTFROM - mailbox in first From address        
       
        SORTSUBJECT - message subject        
       
        SORTTO - mailbox in first To address        
       
        SORTCC - mailbox in first cc address        
       
        SORTSIZE - size of message in octets
       
    
     The flags are a bitmask of one or more of the following: