php判断当前是 http还是 https

**
 * 判断是否SSL协议
 * @return boolean
 */
function is_ssl() {
    if(isset($_SERVER['HTTPS']) && ('1' == $_SERVER['HTTPS'] || 'on' == strtolower($_SERVER['HTTPS']))){
        return true;
    }elseif(isset($_SERVER['SERVER_PORT']) && ('443' == $_SERVER['SERVER_PORT'] )) {
        return true;
    }
    return false;
}

使用

$http = 'http://';
$http =is_ssl()?'https://':$http;