Export to CSV – Headers Question

Hi There –

I’ve got a page with php code that exports results of a DB query into CSV.

So, the workflow is this:

1. Visitor uses a query form and submits query
2. User redirected to query results page, which has a “Save to CSV” link
3. When they click the link, user redirects to a page which executes the CSV creation using the following code:

[insert_php] 

    //Processes the querystring
    $haulIDvar = $_GET['HaulList'];
    $speciesvar = $_GET["SpeciesList"];
    $stationsvar = $_GET["StationList"];
    $datesvar = $_GET["DateList"];

global $wpdb;

//THe if then below evaluates whether or not to export a HAUL WQ Table or a SPECIES Table based on the querystring values

if ($datesvar =="%" && $stationsvar == "%" && $speciesvar == "%" && $haulIDvar != "%")

{
     //Query for Haul Water Quality Table
     $exportList= $wpdb->get_results("SELECT Trawling_Weather_Data.*, Trawling_Logistics.* FROM Trawling_Weather_Data INNER JOIN Trawling_Logistics ON Trawling_Weather_Data.Trawl_Date = Trawling_Logistics.Trawl_Date WHERE Trawling_Weather_Data.HAUL_ID LIKE '" . $haulIDvar . "'" ); 

     //processes the query results

     //Creates CSV
     // Set header row values
     $csv_fields=array();
     $csv_fields[] = 'Field Name 1';
     $csv_fields[] = 'Field Name 2';

}

else

{

//Query for Species Table
$exportList= $wpdb->get_results("SELECT Trawling_Species_Data.*, Trawling_Weather_Data.Station FROM Trawling_Species_Data INNER JOIN Trawling_Weather_Data ON Trawling_Species_Data.Haul_ID = Trawling_Weather_Data.HAUL_ID WHERE Trawling_Species_Data.Species LIKE '" . $speciesvar . "' AND Trawling_Weather_Data.Station LIKE '" . $stationsvar . "' AND Trawling_Species_Data.Haul_ID LIKE '" . $haulIDvar . "' AND Trawling_Weather_Data.Trawl_Date LIKE '" . $datesvar . "'ORDER By Trawl_Date DESC" ); 

//processes the query results
//Creates CSV
     // Set header row values
     $csv_fields=array();
     $csv_fields[] = 'Field Name 1';
     $csv_fields[] = 'Field Name 2';

}
     $output_filename = 'MyDataTable.csv';
     $output_handle = @fopen( 'php://output', 'w' );

     header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0' );
     header( 'Content-Description: File Transfer' );
     header( 'Content-type: text/csv' );
     header( 'Content-Disposition: attachment; filename=' . $output_filename );
     header( 'Expires: 0' );
     header( 'Pragma: public' );

     // Insert header row
     fputcsv( $output_handle, $csv_fields );

     // Parse results to csv format
     foreach ($exportList as $Result) {
	$leadArray = (array) $Result; // Cast the Object to an array
	// Add row to file
	fputcsv( $output_handle, $leadArray );
	}

     // Close output file stream
     fclose( $output_handle ); 

[/insert_php]

The problem is that the page is generating the ubiquitous “Warning: Cannot modify header information”

Here’s an example: Link to result

How can I fix the issue?

Thanks in advance.

https://www.ads-software.com/plugins/insert-php/