login php

<?php
if(!empty($_POST['username']) && !empty($_POST['password'])) {
	$username=$_POST['username'];
	$password=$_POST['password'];

	$con=mysql_connect('localhost','root','') or die(mysql_error());
	mysql_select_db('registration') or die("cannot select DB");

	$query=mysql_query("SELECT * FROM reg1 WHERE username='".$username."' AND password='".$password."'");
	$numrows=mysql_num_rows($query);
	if($numrows!=0){
		while($row=mysql_fetch_assoc($query)){
			$dbusername=$row['username'];
			$dbpassword=$row['password'];#
		}

		if($username == $dbusername && $password == $dbpassword){

			session_start();
			$_SESSION['sess_username']=$username;

			/* Redirect browser */
			header("Location: YourBoxHomepage.php");
		}
	}
	else {
		echo "Invalid Username or Password!";
	}
}
else {
	echo "All fields are required!";
}
?>