可以采用机器（电脑）唯一码 + 上传IP + 当前时间戳 + GUID （ + 随机数），然后MD5做为文件名。机器唯一码有电脑的CPU信息和MAC地址，这两个信息需要在linux或unix系统下才能获取吧。

//获取电脑的CPU信息
function OnlyU(){
        $a = '';
        $b = array();
        if(function_exists('exec')){
                if(mailto:!@exec( /all",$b)){
                        return false;
                }
        }elseif(function_exists('system')){
                ob_start();
                if(mailto:!@system( /all")){
                        return false;
                }else{
                }
                $b = ob_get_contents();
                ob_end_clean();
                $b = explode("\n",$b);//print_r($b);
                array_pop($b);
        }else{
                return false;
        }

$all = sizeof($b);
        for($i = 0; $i < $all; $i++){
                if(strpos($b[$i],"Description") !== false){
                        if(strpos($b[$i+1],"Physical Address") !== false){
                                $c = explode(":",$b[$i+1]);
                                $a = trim($c[1]);
                                break;
                        }
                }
        } // End for
        return empty($a)?false:$a;
} // End function OnlyU

//获取网卡的MAC的地址

function getMAC() {
 @exec("ipconfig /all",$array);
 for($Tmpa;$Tmpa<count($array);$Tmpa++){
  if(eregi("Physical",$array[$Tmpa])){
   $mac=explode(":",$array[$Tmpa]);
   return $mac[1];
  }
 }
}

// 生成guid字符串
function guid($separated = true) {
    if (function_exists ( 'com_create_guid' )) {
        $charid = substr ( strtolower ( com_create_guid () ), 1, - 1 );
        if (! $separated)
            return str_replace ( '-', '', $charid );
        else
            return $charid;
    } else {
        // 生成一个随机的md5串, 然后通过分割来 获得guid
        mt_srand ( ( double ) microtime () * 10000 );
        $charid = md5 ( uniqid ( rand (), true ) );
    }
   
    if (! $separated) {
        return $charid;
    }
    $hyphen = chr ( 45 );
    $uuid = substr ( $charid, 0, 8 ) . $hyphen . substr ( $charid, 8, 4 ) . $hyphen . substr ( $charid, 12, 4 ) . $hyphen . substr ( $charid, 16, 4 ) . $hyphen . substr ( $charid, 20, 12 );
    return $uuid;
}