This is the html part of the code for the layout of the login box.
Code: 
<html>
<head><title>Login System By NucleA</title></head>
<body>
<form method=GET action="login.php">
Username: <input type="TEXT" name="Username"><br/>
Password: <input type="TEXT" name="Password"><br/>
<input type="Submit" value="Login">
</body></html>
Code: 
 
<?php
session_start();
 
mysql_connect("YOUR MYSQl SERVER", "MYSQL USERNAME", "MYSQL PASSWORD") or die(mysql_error());
mysql_select_db("Mysql Database") or die(mysql_error());
 
$username=$_GET['Username'];
$password=$_GET['Password'];
$ver=0;
 
$result=mysql_query("SELECT * FROM table") or die(mysql_error());
 
while($row = mysql_fetch_array( $result )) {
 
if($username=$row['Username']){
    $ver=$ver+1;
}
else{
echo "Invalid Username!";
}
 
if($password=$row['Password']){
$ver=$ver+1;
}
else{
echo "Invalid Password!";
}
 
if ($ver=2){
echo "Successfull Login!";
$_SESSION['User']=REGISTERED;
}