yii2导出excel文档，完美解决csv中的逗号问题

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花了一天的时间，遇到各种坑。

借鉴这篇文章实现导出功能：https://www.yiichina.com/tutorial/1839

转载里面的代码时，发现数据里面出现：空格、逗号、就会使excel不正常，做了以下改进解决问题：

1、将空格、换行符之类的替换为空。

2、将英文的逗号替换为中文的逗号。

public static function exportCsv(Array $csv_header, Array $data, $filename='')
    {
        $filename =$filename?$filename:date('Ymd').'.csv'; //设置文件名
        header("Content-type:text/csv");
        header("Content-Disposition:attachment;filename=".$filename);
        header('Cache-Control:must-revalidate,post-check=0,pre-check=0');
        header('Expires:0');
        header('Pragma:public');
        foreach ($csv_header as $k => $v) {
            $csv_header[$k] = iconv('utf-8','gb2312',$v);
        }
        echo implode(',', $csv_header) . "\n";
        $str = '';
        $qian = array(" ","　","\t","\n","\r"); //需要替换的换行符，空格，等。
        foreach($data as $v){
            foreach ($v as $key => $col){
                //$v[$key] = str_replace(" ","",iconv('utf-8','gb2312//IGNORE',$col));
                $v[$key] = str_replace(",","，",$col);  //将英文逗号换成中文逗号
                $v[$key] = str_replace($qian,"",trim(iconv('utf-8','gb2312//IGNORE',$v[$key])));

            }
            $abc = implode(',',$v);
            $str .= $abc. "\n";
        }
        echo $str;
        flush();
    }

2019.4.19日出现提示问题：

Cannot modify header information - headers already sent by 

分析原因：

因为这个是类的函数，而一般调用这个函数方法时都会重复调用，导致重复输出header

解决办法代码：

 public static function exportCsv(Array $csv_header, Array $data, $filename='')
    {

      	static $i = 1;
      	
      
        $filename =$filename?$filename:date('Ymd').'.csv';
      
      	if($i<2){
          header("Content-type:text/csv");
          header("Content-Disposition:attachment;filename=".$filename);
          header('Cache-Control:must-revalidate,post-check=0,pre-check=0');
          header('Expires:0');
          header('Pragma:public');
        }
        foreach ($csv_header as $k => $v) {
            $csv_header[$k] = iconv('utf-8','gb2312',$v);
        }
        echo implode(',', $csv_header) . "\n";
        $str = '';
        $qian = array(" ","　","\t","\n","\r"); //需要替换的换行符，空格，等。
        foreach($data as $v){
            foreach ($v as $key => $col){
                //$v[$key] = str_replace(" ","",iconv('utf-8','gb2312//IGNORE',$col));
                $v[$key] = str_replace(",","，",$col);
                $v[$key] = str_replace($qian,"",trim(iconv('utf-8','gb2312//IGNORE',$v[$key])));

            }
            $abc = implode(',',$v);
            $str .= $abc. "\n";
        }
        echo $str;
        flush();
      
      	$i++;

    }