Untitled

<?php
$dbhost="localhost";
$dbuser="hbs@localhost";
$dbpass="hbs";
$dbname="hotel_booking";
$connection= mysqli_connect($dbhost,$dbuser,$dbpass,$dbname);

if(isset($_POST['username'])){
                $username=$_POST['username'];
                $password=$_POST['password'];

$sql="SELECT * FROM guest WHERE Gst_username='".$username."' AND Gst_password='".$password."' LIMIT 1";
$res=mysqli_query($connection,$sql);
if (mysqli_num_rows($res)==1) {
	echo '<a id="back_button" href="main.php"><button type="button">Back to search</button></a>';
	echo '<br></br>';
echo "You have successfully logged in. " .$username;

exit();
}
else{
	echo '<a id="back_button" href="main.php"><button type="button">Back to search</button></a>';
	echo '<br></br>';
                echo "Invalid Login Information.Please try again.";

                exit();
}
}
?>
<!DOCTYPE html>
<html>
<head>
                <title>quack</title>
</head>
<body>
<div>
<form method="post" action="login.php">
                UserName  : <input type="text" name="username"><br><br>
                Password : <input type="password" name="password"><br><br>
                <input type="submit" value="Log In">

</form>
 </div>
</body>
</html>