<?php

/*

 * 生成随机字符串

 * @param int $length 生成随机字符串的长度

 * @param string $char 组成随机字符串的字符串

 * @return string $string 生成的随机字符串

 */

function str_rand($length = , $char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') {

    if(!is_int($length) || $length < ) {

        return false;

    }

    $string = '';

    for($i = $length; $i > ; $i--) {

        $string .= $char[mt_rand(, strlen($char) - )];

    }

    return $string;

}

echo str_rand(),"<br />";

/*

 * 生成32位唯一字符串

 */

$uniqid = md5(uniqid(microtime(true),true));

echo $uniqid;