[PHP] PHP Session 的 hash

<?php

ini_set('session.hash_function', 'sha1');ini_set('session.hash_bits_per_character', '4');

/******************************* 

128-bit digest (MD5)  
4 bits/char: 32 char SID    
5 bits/char: 26 char SID    
6 bits/char: 22 char SID

160-bit digest (SHA-1)
4 bits/char: 40 char SID    
5 bits/char: 32 char SID    
6 bits/char: 27 char SID

********************************/

session_start();