PHP下载生成的CSV而不是推送到浏览器下载

Question

我有这个功能可以生成CSV并存储在服务器上（这样可以正常工作）但是它没有推送到浏览器供用户下载，有人能看出原因吗？

它还将数据放入多个部分，如;

发票明细

客户详细信息

发票项目

我希望如果将所有数据放在1行而不是3个部分，但不知道如何执行此操作。

功能：

// download invoice csv sheet
if ($action == 'download_csv'){

    header("Content-type: text/csv"); 

    // Connect to the database
    $mysqli = new mysqli(DATABASE_HOST, DATABASE_USER, DATABASE_PASS, DATABASE_NAME);

    // output any connection error
    if ($mysqli->connect_error) {
        die('Error : ('.$mysqli->connect_errno .') '. $mysqli->connect_error);
    }

    $tables = array('invoices', 'customers', 'invoice_items'); // array of tables need to export

    $file_name = 'invoice-export-'.date('d-m-Y').'.csv';   // file name
    $file_path = 'downloads/'.$file_name; // file path

    $file = fopen($file_path, "w"); // open a file in write mode
    chmod($file_path, 0777);    // set the file permission

    // loop for tables
    foreach($tables as $table) {
        $table_column = array();
        $query_table_columns = "SHOW COLUMNS FROM $table";

        // fetch table field names
        if ($result_column = mysqli_query($mysqli, $query_table_columns)) {
            while ($column = $result_column->fetch_row()) {
                $table_column[] = $column[0];
            }
        }

        // Format array as CSV and write to file pointer
        fputcsv($file, $table_column, ",", '"');

        $query_table_columns_data = "SELECT * FROM $table";

        if ($result_column_data = mysqli_query($mysqli, $query_table_columns_data)) {

            // fetch table fields data
            while ($column_data = $result_column_data->fetch_row()) {
                $table_column_data = array();
                foreach($column_data as $data) {
                    $table_column_data[] = $data;
                }

                // Format array as CSV and write to file pointer
                fputcsv($file, $table_column_data, ",", '"');
            }
        }
    }

    // close file pointer
    fclose($file);

    // ask either save or open
    header("Pragma: public");
    header("Expires: 0");
    header("Content-Type: application/octet-stream");
    header("Content-Disposition: attachment; filename='{$file_name}';" );
    header("Content-Transfer-Encoding: binary");

    // open a saved file to read data
    $fhandle = fopen($file_path, 'r');
    fpassthru($fhandle);
    fclose($fhandle);
    $mysqli->close();
    die;

}

JS

function downloadCSV(action) {

        jQuery.ajax({

            url: 'response.php',
            type: 'POST',
            data: action,
            dataType: 'json',
            success: function(data){
                $("#response .message").html("<strong>Success</strong>: CSV has been successfully generated and also been stored in the downloads/ directory.");
                $("#response").removeClass("alert-warning").addClass("alert-success").fadeIn();
                $("html, body").animate({ scrollTop: $('#response').offset().top }, 1000);
            },
            error: function(data){
                $("#response .message").html("<strong>Error</strong>: Oppps there has been a problem, please try again.");
                $("#response").removeClass("alert-success").addClass("alert-warning").fadeIn();
                $("html, body").animate({ scrollTop: $('#response').offset().top }, 1000);
            } 
        });

    }