login portal

<?php
   session_start();

/*
 * Copyright 2016 James.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

 //login checks given info against the database
    function login(){
        $user = $_POST['username'];
        $password = $_POST['password'];

        //get db data

        $db = new PDO('mysql:host=localhost;dbname=dbname;charset=utf8', 'user', 'password');
        $stmt = $db->prepare('SELECT * FROM login_info WHERE username=:user AND password=:pass AND usergroup=:group AND beta=:beta');
        // Perform queries
        $stmt->bindValue(':id', $db_user, PDO::PARAM_STR);
        $stmt->bindValue(':pass', $db_password, PDO::PARAM_STR);
        $stmt->bindValue(':group', $db_usergroup, PDO::PARAM_STR);
        $stmt->bindValue(':beta', $db_beta, PDO::PARAM_INT);
        $stmt->execute();
        $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

        //check user data against the database
        if($db_user == $user && $db_password == $password){
            //set session

            $_SESSION['logstat'] = true;
            $_SESSION['group'] = $db_usergroup;
            $_SESSION['beta'] = $db_beta;
        }
    }

?>

<!doctype html>
<html>
    <head>
        <title>PWStats | Home</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
    </head>

    <body>
        <p>This is text.</p>

        <form action="login.php" method="post">
            <fieldset>
                <legend>Login</legend>
                User Name:<br>
                <input type="text" name="username"><br>
                Password:<br>
                <input type="password" name="password"><br>
                <input type="submit" value="Submit">
            </fieldset>
        </form>

    </body>
</html>