too long

So I'm trying to get my value from a SELECT tag in HTML, I'm working with the POST method. Somehow when I get my answer back I only get my label, instead of getting my value which is what I need. I manage my form in 3 diferent documents, here is my php doc, the visual part

<form action="actions_admin/demografica_asig.php" method="POST">
<div class="large-4 columns">
            <label>Seleccione Periodo: 
                <select name="selec_periodo">
                    <option value="1">I</option>
                    <option value="2">II</option>
                    <option value="3">III</option>
                    <option vslue="4">IV</option>
                </select>
            </label>
    </div>
</form>

my accion docmuent:

<?php 
    require_once("../../clases/demoasig.class.php");
$selec_periodo = $_POST['selec_periodo'];

$demoasig = new Demografica();
$demoasig->selec_periodo = $selec_periodo; 
$resultdatos = $demoasig->demo_asig();
    echo $resultdatos;
?>

my Class Document:

<?php 
    require_once('conexion.class.php');
    class Demografica{
public $selec_periodo;

public function __construct(){
            $this->asig = array();
        }

public function demo_asig(){
            $sql= "SELECT COUNT(*) FROM est_asig WHERE est_asig_trimestre={$this->selec_periodo}";
$resultado = mysql_query($sql, Conectar::conexion()) or die($sql);

            $this->asig[]= $resultado;

            return $this->asig;
        }

}
 ?>