PHP 强制性文件下载功能的函数代码(任意文件格式)

/********************
*@file - path to file
*/
function force_download($file)
{
if ((isset($file))&&(file_exists($file))) {
header("Content-length: ".filesize($file));
header(Content-Type: application/octet-stream);
header(Content-Disposition: attachment; filename=" . $file . ");
readfile("$file");
} else {
echo "No file selected";
}
}