<?php
    if (!isset($_SESSION['id'],$_SESSION['user'],$_SESSION['email'])) {
        if ($_POST) {
            include('core/models/class.Acceso.php');
            $acceso = new Acceso();
            $acceso->Registrar();
            exit;
        }else{
            $template = new Smarty();
            $template->display('public/registro.tpl');
        }
    }else{
        header('location: ?view=index');
    }
?>

public function Registrar(){
    try {
        if (!empty($_POST['user']) and !empty($_POST['pass']) and !empty($_POST['email'])) {
            $db = new Conexion();
            $this->user = $db->real_escape_string($_POST['user']);
            $this->user = $db->real_escape_string($_POST['email']);
            $this->pass = $this->Encrypt($_POST['pass']);

            $sql = $db->query("SELECT * FROM user WHERE user='$this->user' OR email='$this->email'; ");

            if ($db->rows($sql) == 0) {
                $sql2 = $db->query("INSERT INTO user (user,pass,email) VALUES ('$this->user','$this->pass','$this->email');");
                $sql3 = $db->query("SELECT MAX(id) AS id FROM user;");
                $id = $db->recorrer($sql3);
                $_SESSION['id'] = $id[0];
                $_SESSION['user'] = $this->user;
                $_SESSION['email'] = $this->email;
                // if ($_POST['session'] == true ) {ini_set('session.cookie_lifetime',time() + (60*60*24*2) ); }
                echo 1;
                $db->liberar($sql2,$sql3);
            }else{
                $datos = $db->recorrer($sql);
                if (strtolower($this->user) == strtolower($datos['user']) ) {
                    throw new Exception(2);
                }else{
                    throw new Exception(3);
                }
            }
            $db->liberar($sql);
            $db->close();
        }else{
            throw new Exception("Error : Datos Vacios");

        }
    } catch (Exception $reg) {
        echo $reg->getMessage();
    }
}

<script>
    window.onload = function(){
      document.getElementById('send_request').onclick = function(){

        var connect, user, pass, email, form, result;
        user = document.getElementById('user').value;
        pass = document.getElementById('pass').value;
        email = document.getElementById('email').value;

        if (user != '' && pass != '' && email != '') {
          form ='user=' + user + '&pass=' + pass + '&email=' + email;

          connect = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
          connect.onreadystatechange = function(){
            if (connect.readyState == 4 && connect.status == 200) {
                // console.log(connect.responseText);
              if (parseInt(connect.responseText) == 1) {
                result = '<div class="alert alert-dismissible alert-success" style="width: 500px;"> ';
                result += '<button type="button" class="close" data-dismiss="alert">&times;</button>';
                result += '<strong>Registro Completado></strong> Bienvenidos, solo un poco mas ';
                result += '</div>';
                location.href = '?view=index';
                document.getElementById('_AJAX_').innerHTML = result;
              }else if (parseInt(connect.responseText) == 2) {
                result = '<div class="alert alert-dismissible alert-success" style="width: 500px;"> ';
                result += '<button type="button" class="close" data-dismiss="alert">&times;</button>';
                result += '<strong>ERROR: </strong>El usuario ya existe ';
                result += '</div>';
                document.getElementById('_AJAX_').innerHTML = result;
              }else {
                result = '<div class="alert alert-dismissible alert-success" style="width: 500px;"> ';
                result += '<button type="button" class="close" data-dismiss="alert">&times;</button>';
                result += '<strong>ERROR: </strong>El Email ya existe ';
                result += '</div>';
                document.getElementById('_AJAX_').innerHTML = result;
              }
            }else if(connect.readyState != 4){
              result = '<div class="alert alert-dismissible alert-warning" style="width: 500px;"> ';
                result += '<button type="button" class="close" data-dismiss="alert">&times;</button>';
                result += 'Procesando... ';
                result += '</div>';
                document.getElementById('_AJAX_').innerHTML = result;
            }
          }
          connect.open('POST','?view=reg',true);
          connect.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
          connect.send(form);
        }else{
          result = '<div class="alert alert-dismissible alert-warning" style="width: 500px;"> ';
          result += '<button type="button" class="close" data-dismiss="alert">&times;</button>';
          result += '<strongERROR></strong> Todos los Campos Deben estar llenos ';
          result += '</div>';
          document.getElementById('_AJAX_').innerHTML = result;
        }
      }
    }
  </script>