เปลี่ยน MySql เป็น Mssql แต่ไม่ทราบว่าต้องเขียนยังไงค่ะ

<?php
// Database
define('DB_HOST', 'localhost\sqlexpress');
define('DB_NAME', 'northwind');
define('DB_USER', '');
define('DB_PASSWORD', '');
define('DB_CHARACTERSET', 'UTF-8');

$connection_info = array("UID" => DB_USER,
   "PWD" => DB_PASSWORD,
   "Database" => DB_NAME,
   "CharacterSet" => DB_CHARACTERSET);

$conn = sqlsrv_connect(DB_HOST, $connection_info);

if ($conn === FALSE) {
   echo "Unable to connect.<br />";
   die(print_r(sqlsrv_errors(), TRUE));
}

$query = "SELECT EmployeeID, FirstName, LastName FROM Employees WHERE EmployeeID BETWEEN ? AND ? OR EmployeeID = ? OR FirstName = ?";
$params = array(2, 5, 7, 'M%');

$result= sqlsrv_query($conn, $query, $params);

if ($result === FALSE) {
   echo "Error in executing query.<br />";
   die(print_r(sqlsrv_errors(), TRUE));
}

while ($row = sqlsrv_fetch_array($result)) {
   foreach ($row as $key => $value) {
      echo $key . "=" . $value . "<br />";
   }

   echo "<br />";
}
?>

// Database
define('SQLSRV_HOST', 'localhost\sqlexpress');
define('SQLSRV_NAME', 'northwind');
define('SQLSRV_USER', '');
define('SQLSRV_PASSWORD', '');

$dns = "sqlsrv:Server=" . SQLSRV_HOST . ";Database=" . SQLSRV_NAME . ";";
$dbh = new PDO($dns, SQLSRV_USER, SQLSRV_PASSWORD);
        
$query = "SELECT EmployeeID, FirstName, LastName FROM Employees WHERE EmployeeID BETWEEN :employeeID1 AND :employeeID2 OR EmployeeID = :employeeID3 OR FirstName = :FirstName";
$stmt = $dbh->prepare($query);
$stmt->bindParam(':employeeID1', 2, PDO::PARAM_INT);
$stmt->bindParam(':employeeID2', 5, PDO::PARAM_INT);
$stmt->bindParam(':employeeID3', 7, PDO::PARAM_INT);
$stmt->bindParam(':FirstName', 'M%', PARAM_STR);
$stmt->execute();

while ($result = $stmt->fetch(PDO::FETCH_ASSOC)) {
   foreach ($result as $key => $value) {
      echo $key . "=" . $value . "<br />";
   }
 
   echo "<br />";
}