<?php


if(isset($_SESSION['is_login']))
{
    header('Location:index.php');
    exit;
}

if(!empty($_POST))
{
    $query="SELECT * FROM staff WHERE username ='{$_POST['username']}' AND password ='{$_POST['username']}'";
    $result=mysql_query($query);


    if(is_array($result))
    {
        $_SESSION = $result[0];
        $_SESSION['is_login'] = true;


    }
    else
    {
        $status = '<p style="background-color: red; color: white;">
                    Invalid username / password</p>';
    }

}
?>

<form action="login.php" method="">
    <input type="text" name="username" value="">
    <input type="password" name="password" value="">
    <input type="submit" value="login">
</form>

<?php
if (isset($status))
    echo $status;
?>