主要是获取主域名，自动识别证书，https://www.csdn.net/
可以当普通的函数，或者在框架中添加函数用
function getHostDomain()
{
// return $_SERVER['REQUEST_SCHEME'] . '://' . $_SERVER['SERVER_NAME'];
return getHttpType() . $_SERVER['SERVER_NAME'];
}
/**
* 获取 HTTPS协议类型
* @return string
*/
function getHttpType()
{
return $type = ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') || (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https')) ? 'https://' : 'http://';
}