Untitled

<!DOCTYPE html>
<html>
<head>
    <?php
    $_SESSION['num1']=$_POST['num1'];
    $_SESSION['num2']=$_POST['num2'];
    $_SESSION['Operator']=$_POST['Operator'];


   $x= $_SESSION['num1'];
   $y= $_SESSION['num2'];
   $z= $_SESSION['Operator'];
     ?>
</head>
<body>


    <?php echo $x; ?>

    <?php echo $y; ?>

    <?php if ($z = 'add')
    $w = $x + $y;
    else if ($z = 'subtract')
    $w = $x - $y;
    else if ($z = 'times')
    $w = $x * $y;
     else if ($z = 'divide')
    $w = $x / $y;
    else {
    $w = 'undefined';}
    echo $w;

    ?>
</body>
</html>