实现“下载文件”功能

验证用户权限后调用此函数可以下载文件，文件可以放在任意位置。
客户端不会出现乱码
不会知道所下载文件真实路径。


/**
* 下载文件
* @param string $file
* 被下载文件的路径
* @param string $name
* 用户看到的文件名
*/
function download($file,$name=''){
$fileName = $name ? $name : pathinfo($file,PATHINFO_FILENAME);
$filePath = realpath($file);

$fp = fopen($filePath,'rb');

if(!$filePath || !$fp){
header('HTTP/1.1 404 Not Found');
echo "Error: 404 Not Found.(server file path error)";
exit;
}

$fileName = $fileName .'.'. pathinfo($filePath,PATHINFO_EXTENSION);
$encoded_filename = urlencode($fileName);
$encoded_filename = str_replace("+", "%20", $encoded_filename);

header('HTTP/1.1 200 OK');
header( "Pragma: public" );
header( "Expires: 0" );
header("Content-type: application/octet-stream");
header("Content-Length: ".filesize($filePath));
header("Accept-Ranges: bytes");
header("Accept-Length: ".filesize($filePath));

$ua = $_SERVER["HTTP_USER_AGENT"];
if (preg_match("/MSIE/", $ua)) {
header('Content-Disposition: attachment; filename="' . $encoded_filename . '"');
} else if (preg_match("/Firefox/", $ua)) {
header('Content-Disposition: attachment; filename*="utf8\'\'' . $fileName . '"');
} else {
header('Content-Disposition: attachment; filename="' . $fileName . '"');
}

// ob_end_clean(); // 输出文件内容
fpassthru($fp);
exit;
}

AD：真正免费，域名+虚机+企业邮箱=0元