Untitled

<?php

 ?>


<!DOCTYPE html>
<html lang="es">
<head>
<meta charset="utf-8">
<title>Login</title>

</head>
<body>
<div>
<center>
    <form method="POST" action="validar.php">
    <input type="text" name="nombre" placeholder="Usuario">
    <br>
    <input type="password" name="password" placeholder="Contraseña"><br>
    <button type="submit">Iniciar Sesion</button>

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

<?php
include 'conex.php';
$usuario = $_POST['nombre'];
$pass = $_POST['password'];

if(empty($usuario) || empty($pass)){
header("Location: index.php");
exit();
}
$query=("SELECT * FROM usuarios where Username='".$usuario."'");
echo var_dump($query);
$res = $con->query($query);
if($row = mysql_fetch_array($res)){
if($row['Password'] == $pass){
session_start();
$_SESSION['usuario'] = $usuario;
header("Location: inicio.php");
}
else
{
header("Location: index.php");
exit();
}
}
else
{
header("Location: index.php");
exit();
}
?>

if (empty($usuario) || empty($pass)) {
    header("Location: index.php");
    exit();
}

if (!isset($_SESSION)) {
    session_start();
}
if (isset($_SESSION['usuario'])) {
    header("Location: inicio.php");
} else {
    // Sentencias...
}

<label id="uno">Inicio de Sesión</label>
        <fieldset style="width:400px" id="cuadro">
            <form action="" method="post">
            <br>
            <label id="dos" for="username">Username: </label><input type="text" id="username" name="username" >
            <br><br>
            <label id="tres"for="pass">Password: </label><input type="password" id="pass" name="pass" >
            <br><br>
            <input type="submit" value="Iniciar Sesión" class="btn btn-primary">&nbsp&nbsp <input type="reset" value="Limpiar" class="btn btn-primary">
            </form>
        </fieldset>
    </center>
        <?php
            if(!empty($_POST['username'])){

                include "Conex.php";
                include "User.php";
                $conex = new ConexionDB;
                $user = User::login(addslashes($_POST['username']),$_POST['pass'],$conex);
                //$userData=$user->getReturn();
                $userData=$user;
                if( !empty($userData) ){
                    session_start();
                    $_SESSION['user']=$userData;
                    header('location:home.php');
                }else{
                    echo "<br>";
                    echo "<center><h3>Username o password incorrectos!</h3></center>";
                }
            }
        ?>