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<?php
session_start();
include("login.php");

$host="localhost";
$username ="root";
$password="";
$db_name="users";
$tbl_name="users_info";

$mysql_connect($host, $username,$password)or die(mysql_error());
$mysql_select_db()or die(mysql_error());

$myusername = mysql_real_escape_strings($_GET['username']);
$mylastname = mysql_real_escape_strings($_GET['password']);

$sql="Select * FROM $tbl_name WHERE username='$username' and password='$password'";
$result=mysql_query($sql);

if(mysql_num_rows($result) = 1)
{
    $_SESSION['logged_in'] = true;
}
else
{
    $_SESSION_['logged_in'] = false;
}
?>
<html>
<head>
<body>
<?php if($_SESSION['logged_in'] === true){
echo "
<input type="text" name="username" />
<br />
<input type="password" name="password" />
<input type="submit" value="submit" />
</form>
";
}
else
{
echo "You are already logged in";
}