PHP 다운로드 파일이 깨졌을 경우 어떻게 해야 하나요?

<?php
/**
 * 强制下载文件
 * @param string $filename 变量
 * @param string $name 变量
 * @return mixed
 */
function download($filename,$name){
  if ((isset($filename))&&(file_exists($filename))){
     header("Content-length: ".filesize($filename));
     header(&#39;Content-Type: application/octet-stream&#39;);
     header(&#39;Content-Disposition: attachment; filename="&#39; . $name . &#39;"&#39;);
     ob_clean();  
     flush();
     readfile("$filename");
  } else {
     $info="Looks like file does not exist!";
     return $info;
  }
}
?>