discuz函数解析--写日志

    public static function writelog($file, $log) {
        global $_G;
        $yearmonth = dgmdate(TIMESTAMP, 'Ym', $_G['setting']['timeoffset']);
        $logdir = DISCUZ_ROOT.'./data/log/';
        $logfile = $logdir.$yearmonth.'_'.$file.'.php';
        if(@filesize($logfile) > 2048000) { //判断文件大小，如果超过2M，则将日志文件重命名
            $dir = opendir($logdir);
            $length = strlen($file);
            $maxid = $id = 0;
            while($entry = readdir($dir)) {
                if(strpos($entry, $yearmonth.'_'.$file) !== false) {
                    $id = intval(substr($entry, $length + 8, -4));
                    $id > $maxid && $maxid = $id;
                }
            }
            closedir($dir);

            $logfilebak = $logdir.$yearmonth.'_'.$file.'_'.($maxid + 1).'.php';
            @rename($logfile, $logfilebak);
        }
        if($fp = @fopen($logfile, 'a')) {
            @flock($fp, 2);//文件锁
            if(!is_array($log)) {
                $log = array($log);
            }
            foreach($log as $tmp) {
                fwrite($fp, "<?PHP exit;?>\t".str_replace(array('<?', '?>'), '', $tmp)."\n");
            }
            fclose($fp);
        }
    }

dz的写日志函数，重用性还可以。