1. 首先在function.php里面新增以下代码：路径：/usr/themes/Joe/core/function.php

//在线人数
function online_users() {
    $filename='online.txt'; //数据文件
    $cookiename='Nanlon_OnLineCount'; //Cookie名称
    $onlinetime=30; //在线有效时间
    $online=file($filename); 
    $nowtime=$_SERVER['REQUEST_TIME']; 
    $nowonline=array(); 
    foreach($online as $line){ 
        $row=explode('|',$line); 
        $sesstime=trim($row[1]); 
        if(($nowtime - $sesstime)<=$onlinetime){
            $nowonline[$row[0]]=$sesstime;
        } 
    } 
    if(isset($_COOKIE[$cookiename])){
        $uid=$_COOKIE[$cookiename]; 
    }else{
        $vid=0;
        do{
            $vid++; 
            $uid='U'.$vid; 
        }while(array_key_exists($uid,$nowonline)); 
        setcookie($cookiename,$uid); 
    } 
    $nowonline[$uid]=$nowtime;
    $total_online=count($nowonline); 
    if($fp=@fopen($filename,'w')){ 
        if(flock($fp,LOCK_EX)){ 
            rewind($fp); 
            foreach($nowonline as $fuid=>$ftime){ 
                $fline=$fuid.'|'.$ftime."\n"; 
                @fputs($fp,$fline); 
            } 
            flock($fp,LOCK_UN); 
            fclose($fp); 
        } 
    } 
    echo "$total_online"; 
}