功能转换为excel不工作在线wp

Question

我使用此代码从wordpress数据库创建一个excel文件。它在localhost上运行得非常好，但是当我在真实的网站上试用它时，它只会打开一个显示标题的新选项卡。我是否缺少一段代码来阻止按钮这样做？

function get_excel()
{
    if (isset($_POST['excel'])) {
        if (isset($_SESSION['id'])) {
            $id = $_SESSION['id'];
        }
       // echo 'werkt';
        global $wpdb, $post;
        $file = "orders";
        $tblorders= $wpdb->prefix.'b2borders';
        $output1="";
        $output="";

        $column_name = array('voornaam','familienaam','leveradress','land','product','maat','aantal','prijs');
        foreach ($column_name as $caname) {
            $output .= $caname . "\t";
        }
        print $output;
        $landen = $wpdb->get_results("SELECT DISTINCT land FROM `wp_b2borders` WHERE domainid=$id ORDER BY `wp_b2borders`.`land` ASC");
        foreach ($landen as $l)
        {
            $unewline = "\r\n";
            if (strstr(strtolower($_SERVER['HTTP_USER_AGENT']), 'win')) {
                $unewline = "\r\n";
            } else if (strstr(strtolower($_SERVER['HTTP_USER_AGENT']), 'mac')) {
                $unewline = "\r";
            } else {
                $unewline = "\n";
            }
            $output3 = $unewline.$l->land;
            print $output3;
            $land = $l->land;
            $expid = "SELECT * FROM $tblorders WHERE domainid = $id AND land = '$land' ";
            $expids = $wpdb->get_results($expid);
            $totprijs=0;


            foreach ($expids as $t) {
                $vn = $t->voornaam;
                $fn = $t->famnaam;
                $la = $t->land;
                $adress = $t->leveradress;
                $product=$t->product;
                $aa=$t->aantal;
                $maat = $t->maat;
                $prijs = $t->prijs;
                $pr = $prijs*$aa;
                $totprijs +=$pr;
                $output1 = $unewline . strip_tags($vn) . "\t" . strip_tags($fn) . "\t" . strip_tags($adress) . "\t". strip_tags($la) . "\t" . strip_tags($product) . "\t" . strip_tags($maat) . "\t". strip_tags($aa) . "\t". strip_tags($pr) . "\t" ;
                print $output1;
            }
            print $unewline.'totaalprijs '.$land.': '.$totprijs;

        }

        $filename = $file . "_" . date('Y-m-d_H-i', time());
        header('Content-Type: application/vnd.ms-excel');
        header('Content-Disposition: attachment;filename="'.$filename.'.xls"');
        header('Cache-Control: max-age=0');

//            $url = 'admin.php?page=my_pirazzo_edit&id=' . $id;
//            wp_redirect($url);
        exit;
    }
}