<?php

$view = new stdClass();
$view->pageTitle = 'Calculator';
require_once('Models/Calculator.php');

if(isset($_POST['submit'])) {
    $calculator = new Calculator($_POST['expression']);
    $value = $calculator->calculate();
    if (!$value) {
        $view->result = "Invalid Number";
    }
    else {
        $view->result = 'The result is ' . $value;
    }
}

require_once('Views/calculator.phtml');