php 获取随机字符串算法

function get_rand_str($randLength=6,$addtime=1,$includenumber=0){
    if ($includenumber){
        $chars='abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQEST123456789';
    }else {
        $chars='abcdefghijklmnopqrstuvwxyz';
    }
    $len=strlen($chars);
    $randStr='';
    for ($i=0;$i<$randLength;$i++){
        $randStr.=$chars[rand(0,$len-1)];
    }
    $tokenvalue=$randStr;
    if ($addtime){
        $tokenvalue=$randStr.time();
    }
    return $tokenvalue;
}