OrcHelper.class.php on line 13

各位求帮忙，第十三行错误

class OrcHelper
{
public $conn;
public $host="localhost/test";
public $username="root";
public $password="root";

public function __construct()
{
    date_default_timezone_set("Asia/Shanghai");
    $this->conn=oci_connect($this->username,$this->password,$this->host,"utf8");
    if(!$this->conn)
    {
        die("连接失败".oci_error($this->conn));
    }
}

Fatal error: Call to undefined function oci_connect() in D:\phpStudy\WWW\sc\conf\class\OrcHelper.class.php on line 13

oci_connect 未定义，phpinfo或者php.ini中看看php的Oracle插件开启了没有