Código PHP:
<?php
$form = '<form action="loogin.php" method="post">
Usuario: <input type="text" name="user"><br>
Contraseña: <input type="password" name="pass"><br>
<input type="submit" name="enviar" value="Entrar">
</form>';
if(isset($_POST["enviar"])){
if(($_POST["user"] == "martin") and ($_POST["pass"] == "4113")){
$url = "privada/inicio.html";
$delay = "0.1";
$cadena .= '<meta http-equiv="refresh" content="'.$delay.'; url='.$url.'">';
echo $cadena;
}else{
echo "<script language=JavaScript>alert('El usuario no es Correcto.');</script>";
}
}else{
print $form;
}
?>