php默认是没有开启连接 Microsoft SQL Server 的，需要自己去配置安装启用
安装驱动（以windows系统为例）
1、打开 php.net，搜索关键词 sqlsrv
2、点击「安装」链接，找到驱动下载地址，这里我用的是php7.0，所以链接为 https://docs.microsoft.com/zh-cn/sql/connect/php/microsoft-php-driver-for-sql-server
3、根据下述指导来下载对应的exe
Requires PHP 7 or 5.x. For information about how to download and install the latest stable binaries, visit http://windows.php.net for more detail.
- Version support for PHP is as follows
- Version 4.0 supports PHP 7.0+ on Windows and Linux
- Version 3.2