无法修改静态功能上的标题信息 [英] Cannot modify header information on Static Function

问题描述

我想要做的是调用一个类将mysql数据导出到另一个类的excel中。下面是我用过的代码（我省略了打开连接的代码）：

  //这是用于调用`ExportToExcel`类的类
类SampleClass {
 public static function mainFunction（）{
 ExportToExcel :: exportToExcel（）; 
 
 
 
类ExportToExcel {
 public static function exportToExcel（）{
 $ DB = DB :: Open（）; //打开数据库
 
 $ csv_terminated =\\\
; 
 $ csv_separator =，; 
 $ csv_enclosed =''; 
 $ csv_escaped =\\; 
 
 $ sql_query =查询到这里......; 
 
 $ result = $ DB-> qry（$ sql_query，2，TRUE）; //运行查询
 $ fields_cnt = 0; 
 $ schema_insert =''; 
 
 while（$ finfo = mysqli_fetch_field（$ result））{
 $ fields_cnt ++; 
 $ l = $ csv_enclosed。str_replace（$ csv_enclosed，$ csv_escaped。$ csv_enclosed，stripslashes（$ finfo-> ; name））。$ csv_enclosed; 
 $ schema_insert。= $ l; 
 $ schema_insert。= $ csv_separator; 
} 
 
 $ out = trim（substr（ $ $ $ $。$ = $ csv_terminated; 
 
 while（$ row = mysqli_fetch_array（$ result））{
 $ schema_insert ='' ; 
 for（$ j = 0; $ j <$ fields_cnt; $ j ++）{
 if（$ row [$ j] =='0'|| $ row [$ j]！= ''）{
 if（$ csv_enclosed ==' '）$ schema_insert。= $ row [$ j]; 
 else {
 $ schema_insert。= $ csv_enclosed。 
 str_replace（$ csv_enclosed，$ csv_escaped。$ csv_enclosed，$ row [$ j]）。 $ csv_enclosed; 
} 
} else $ schema_insert。=''; 
 
 if（$ j <$ fields_cnt  -  1）$ schema_insert。= $ csv_separator; 
} 
 
 $ out。= $ schema_insert; 
 $ out。= $ csv_terminated; 
 
 
 header（Cache-Control：must-revalidate，post-check = 0，pre-check = 0）; //  - >警告
 header（Content-Length：。strlen（$ out））; //  - >警告
标题（Content-type：text / x-csv）; //  - >警告
 header（Content-Disposition：attachment; filename = somefile.csv）; //  - >警告
 echo $ out; 
出口; 
 
 
  

但它返回错误：

 警告：无法修改标题信息 - 已经发送的标题（输出始于XX行'文件'中的输出
  

当我直接运行代码而没有任何类和函数时，它可以正常工作。我试着用 var_dump来检查标题列表（headers_list（））和我有：

  array（5）{
 [0] => string（23）X-Powered-By：PHP / 5.4.4
 [1] => string（38）Expires：Thu，1981年11月19日08:52： 00 GMT
 [2] => string（77）Cache-Control：no-store，no-cache，must-revalidate，post-check = 0，pre-check = 0
 （3）=>字符串（16）Pragma：no-cache
 [4] =>字符串（23）Content-type：text / html
} 
  

我试着用 header_remove（）; 但它是一样的。如何解决这个问题？谢谢...

解决方法

尝试在开始处添加 ob_start（），并在结尾处添加 ob_flush（） p>

What I want to do is, calling a class for exporting mysql data to the excel from another class. Below is the code I've used (I've omitted the code for opening the connection):

//This is the class for calling the `ExportToExcel` class
Class SampleClass {
    public static function mainFunction() {
        ExportToExcel::exportToExcel();
    }
}

Class ExportToExcel {
    public static function exportToExcel() {
        $DB = DB::Open(); //Open the database

       $csv_terminated = "\n";
       $csv_separator = ",";
       $csv_enclosed = '"';
       $csv_escaped = "\\";

       $sql_query = "The Query goes here...";

       $result = $DB->qry($sql_query, 2, TRUE); //Run the query 
       $fields_cnt = 0;
       $schema_insert = '';

       while ($finfo = mysqli_fetch_field($result)) {
           $fields_cnt++;
           $l = $csv_enclosed . str_replace($csv_enclosed, $csv_escaped . $csv_enclosed, stripslashes($finfo->name)) . $csv_enclosed;
           $schema_insert .= $l;
           $schema_insert .= $csv_separator;
       }

       $out = trim(substr($schema_insert, 0, -1));
       $out .= $csv_terminated;

       while ($row = mysqli_fetch_array($result)) {
           $schema_insert = '';
           for ($j = 0; $j < $fields_cnt; $j++) {
               if ($row[$j] == '0' || $row[$j] != '') {
                   if ($csv_enclosed == '') $schema_insert .= $row[$j];
                   else {
                       $schema_insert .= $csv_enclosed . 
                       str_replace($csv_enclosed, $csv_escaped . $csv_enclosed, $row[$j]) . $csv_enclosed;
                   }
               } else $schema_insert .= '';

               if ($j < $fields_cnt - 1) $schema_insert .= $csv_separator;
            }

            $out .= $schema_insert;
            $out .= $csv_terminated;
       } 

       header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); //--> WARNING
       header("Content-Length: " . strlen($out)); //--> WARNING
       header("Content-type: text/x-csv"); //--> WARNING
       header("Content-Disposition: attachment; filename=somefile.csv"); //--> WARNING
       echo $out;
       exit;
    }
}

But it returns error:

Warning: Cannot modify header information - headers already sent by (output started at 'files' on line XX

When I run the code directly without any class and function, it works. I've tried to check the header list using var_dump(headers_list()) and I've got:

array(5) { 
    [0]=> string(23) "X-Powered-By: PHP/5.4.4" 
    [1]=> string(38) "Expires: Thu, 19 Nov 1981 08:52:00 GMT" 
    [2]=> string(77) "Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0" 
    [3]=> string(16) "Pragma: no-cache" 
    [4]=> string(23) "Content-type: text/html" 
}

I've tried to remove the header using header_remove(); but it was the same. How to solve the problem? Thanks...

解决方案

try to add ob_start() at start and ob_flush() at end

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