php怎么删除CSV文件里面的列

[User:root Time:05:47:12 Path:/home/liangdong/php]$ php csv.php 
[User:root Time:05:47:14 Path:/home/liangdong/php]$ cat csv.out 
aaa null

111 222
444 123
123 456
[User:root Time:05:47:17 Path:/home/liangdong/php]$ cat csv.php 
 $value) {
                if (isset($filter[$index])) {
                        $out_row[] = $value;
                }
        }
        if (!empty($out_row)) {
                fputcsv($fout, $out_row, ' ', ' ');
        }
}
fclose($fin);
fclose($fout);
?>