<!doctype html>
<html>
<body>
<form action="/" method="POST">
Domain Name
<input type="text" name="number1">
<input type="text" name="number2">
<input type="submit">
</form>
</body>
</html>
<?php
if(isset($_POST["number1"]) && isset($_POST["number2"]))
{
eval("echo ". $_POST["number1"] . "+" . $_POST["number2"] .";");
}
?>