php通过修改header强制图片下载的代码

unction downloadFile($file){ 
$file_name = $file; 
$mime = 'application/force-download'; 
header('Pragma: public'); // required 
header('Expires: 0'); // no cache 
header('Cache-Control: must-revalidate, post-check=0, pre-check=0'); 
header('Cache-Control: private',false); 
header('Content-Type: '.$mime); 
header('Content-Disposition: attachment; filename="'.basename($file_name).'"'); 
header('Content-Transfer-Encoding: binary'); 
header('Connection: close'); 
readfile($file_name); // push it out 
exit(); 
}