php代码生成txt文件并下载

<?php
    header("Content-Type: application/octet-stream"); 
      
    $quan=$_GET['quan'];
    $ua = $_SERVER["HTTP_USER_AGENT"]; 
    $filename = "100yuan.txt"; 
    $encoded_filename = urlencode($filename); 
    $encoded_filename = str_replace("+", "%20", $encoded_filename); 
      
    if (preg_match("/MSIE/", $_SERVER['HTTP_USER_AGENT']) ) { 
        header('Content-Disposition:  p_w_upload; filename="' . $encoded_filename . '"'); 
    } elseif (preg_match("/Firefox/", $_SERVER['HTTP_USER_AGENT'])) { 
       // header('Content-Disposition: p_w_upload; filename*="utf8' .  $filename . '"');
        header('Content-Disposition: p_w_upload; filename*="' .  $filename . '"'); 
    } else { 
        header('Content-Disposition: p_w_upload; filename="' .  $filename . '"'); 
    }
      
    echo '您已领取100元现金券。现金券编码是：'.$quan;
?>