php生成会员账号

自己用php写的生成会员账号功能，仅供参考，代码如下：

function get_number($table,$filed){
    if(!isset($table) || !isset($filed)){
        return '';
    }
    if(trim($table)=='' || trim($filed)==''){
        return '';
    }
    global $db;
    $user_number=str_shuffle(substr(randomname(-5),11));
    $sql="select `id` from `".$table."` where `".$filed."`='".$user_number."'";
    if($db->getRowsNum($sql) || strpos($user_number,'0')==0){
        get_number($table,$filed);
    }
    return $user_number;
}

/***********生成随机数[随机数是后五位，一共是19位]****************/
function randomname($start,$len=''){
    if(!isset($start) || !is_numeric($start) || ($len!='' && !is_numeric($len))){
        return '';
    }echo '-----';
    $seedstr=explode(' ',microtime(),5); 
    $seed=$seedstr[0]*10000; 
    $random=date('YmdHis', time()).rand(10000,100000);
    return $len===''?substr($random,$start):substr($random,$start,$len);
}