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<?php
$serverName = "DESKTOP-FDJAOMJ\sqlexpress"; //serverNameinstanceName
$connectionInfo = array( "Database"=>"sgo", "UID"=>"arm", "PWD"=>"arm123");
$con = sqlsrv_connect( $serverName, $connectionInfo);

if( $con ) {
     echo "Connection established.<br />";
}else{
     echo "Connection could not be established.<br />";
     die( print_r( sqlsrv_errors(), true));
}
?>

<!DOCTYPE html>
<html>
    <body>
        <?php
        require('db.php');
        session_start();
        // If form submitted, insert values into the database.
        if (isset($_POST['username'])){
                // removes backslashes
            $username = stripslashes($_REQUEST['username']);
                //escapes special characters in a string
            //$username = unpack($con,$username);
            $password = stripslashes($_REQUEST['password']);
            //$password = addslashes($con,$password);
            //Checking is user existing in the database or not
            $query = "SELECT * FROM `users` WHERE username='$username' and password='$password'";
            $params = array();
            $result = sqlsrv_query($con,$query,$params) or die(sqlsrv_errors());
            $rows = sqlsrv_num_rows($result);
                if($rows==1){
                $_SESSION['username'] = $username;
                    // Redirect user to index.php
                header("Location: index.php");
                 }else{
            echo "<div class='form'>
        <h3>Username/password is incorrect.</h3>
        <br/>Click here to <a href='login.php'>Login</a></div>";
            }
            }else{
        ?>
        <div class="form">
            <h1>Log In</h1>
            <form action="" method="post" name="login">
                <input type="text" name="username" placeholder="Username" required />
                <input type="password" name="password" placeholder="Password" required />
                <input name="submit" type="submit" value="Login" />
            </form>
            <p>Not registered yet? <a href='registration.php'>Register Here</a></p>
        </div>
        <?php } ?>
    </body>
</html>