4.13、文件下载

/**
 * 文件下载
 * @param $filepath 文件路径
 * @param $filename 文件名称
 */
function file_down($filepath, $filename = '') {
   if(!$filename) $filename = basename($filepath);
   if(is_ie()) $filename = rawurlencode($filename);
   $filetype = fileext($filename);
   $filesize = sprintf("%u", filesize($filepath));
   if(ob_get_length() !== false) @ob_end_clean();
   header('Pragma: public');
   header('Last-Modified: '.gmdate('D, d M Y H:i:s') . ' GMT');
   header('Cache-Control: no-store, no-cache, must-revalidate');
   header('Cache-Control: pre-check=0, post-check=0, max-age=0');
   header('Content-Transfer-Encoding: binary');
   header('Content-Encoding: none');
   header('Content-type: '.$filetype);
   header('Content-Disposition: attachment; filename="'.$filename.'"');
   header('Content-length: '.$filesize);
   readfile($filepath);
   exit;
}

/**
 * IE浏览器判断
 */
function is_ie() {
    $useragent = strtolower($_SERVER['HTTP_USER_AGENT']);
    if((strpos($useragent, 'opera') !== false) || (strpos($useragent, 'konqueror') !== false)) return false;
    if(strpos($useragent, 'msie ') !== false) return true;
    return false;
}

/**
 * 取得文件扩展
 *
 * @param $filename 文件名
 * @return 扩展名
 */
function fileext($filename) {
    return strtolower(trim(substr(strrchr($filename, '.'), 1, 10)));
}