php下载文件无法打开怎么办

if (file_exists(CACHE_PATH . $file_name)){
 //$this->logger->error('file realpath:'.realpath(CACHE_PATH . $file_name));
 header( 'Pragma: public' );
 header( 'Expires: 0' );
 header( 'Content-Encoding: none' );
 header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0' );
 header( 'Cache-Control: public' );
 header( 'Content-Type: application/vnd.ms-excel'); 
 header( 'Content-Description: File Transfer' );
 header( 'Content-Disposition: attachment; filename=' . $file_name );
 header( 'Content-Transfer-Encoding: binary' );
 header( 'Content-Length: ' . filesize ( CACHE_PATH . $file_name ) );
 readfile ( CACHE_PATH . $file_name );
 } else {
 $this->logger->error('export model :'.$id.' 错误：未生产文件');
 echo '<script>alert('export error, file not exists！')</script>';
 }