php生成随机数或者字符串的代码

/**
*产生随机字符串
*
*产生一个指定长度的随机字符串,并返回给用户
*
*@accesspublic
*@paramint$len产生字符串的位数
*@returnstring
*/
functionrandstr($len=6){
$chars="ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz0123456789-@#~";
//characterstobuildthepasswordfrom
mt_srand((double)microtime()*1000000*getmypid());
//seedtherandomnumbergenerater(mustbedone)
$password="";
while(strlen($password)<$len)
$password.=substr($chars,(mt_rand()%strlen($chars)),1);
return$password;
}