Cannot modify header information on Static Function

Question

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...

`headers already sent by ...` who ? – Mihai Iorga Oct 03 '12 at 07:14 — Mihai Iorga, Oct 03 '12 at 07:14

Drahkar · Answer 1 · 2012-10-03T07:26:30.400

This means that at some point you are sending text to the browser before you do your various header() calls.

Check your code and see if any of it is printing a response to what it is doing. This can be anything from an error from the code or a print of some sort.

Unfortunately without having the complete code we won't be able to identify the specific portion of the code that is sending text to the browser prior to your header() calls.

EDIT:

Also check for white spaces. If you have white spaces outside of the <?php ?> being passed to the browser before the the header() calls, that will do this as well.

score 1 · Accepted Answer · answered Oct 03 '12 at 07:15

1

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

answered Oct 03 '12 at 07:15

Pragnesh Chauhan

8,363
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Absolutely!! =D , I tried to place the code on the really beginning on the page and at the end. It works! Thanks :) – mrjimoy_05 Oct 03 '12 at 07:37
1

use `ob_end_flush()` at the end. – StaticVariable Oct 03 '12 at 07:39
Where is the _start_ and where is the _end_? – Razvan Zamfir Oct 21 '17 at 17:35

score 1 · Answer 3 · edited May 23 '17 at 12:24

1

This problem occurs when we send some output to browser and than header.You should find out a white space or a echo before any header() like header("location").

refer to this article Header already send problem

edited May 23 '17 at 12:24

Community

1
1

answered Oct 03 '12 at 07:38

StaticVariable

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Hi, thanks for the code.. But I'm using `ob_start()` and `ob_end_flush()` as you said and it's work :) – mrjimoy_05 Oct 03 '12 at 07:41

Cannot modify header information on Static Function

3 Answers3

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