生成uuid

create_uuid.php

<?php
// UUID百度百科<http://baike.baidu.com/view/1052579.htm>
// 8-4-4-4-12
function create_uuid()
{
    $str = md5(uniqid('', true));
    return preg_replace('/(\w{8})(\w{4})(\w{4})(\w{4})(\w{12})/', '$1-$2-$3-$4-$5', $str);
}

直观方法：

<?php
// UUID百度百科<http://baike.baidu.com/view/1052579.htm>
// 8-4-4-4-12
function create_uuid()
{
    $str = md5(uniqid('', true));
    $sep = '-';
    return substr($str, 0, 8) . $sep . substr($str, 8, 4) . $sep . substr($str, 12, 4) . $sep . substr($str, 16, 4) . $sep . substr($str, 12);
}