Here's my solution:
<!DOCTYPE html>
<html>
<head>
<title>Sum</title>
</head>
<body>
<form>
<div>Number 1:</div>
<input type="number" name="num1"/>
<div>Number 2:</div>
<input type="number" name="num2"/>
<div><br><input type="submit" value="CHECK THE SUM"></div><br>
</form>
<?php
if (isset($_GET['num1']) && isset($_GET['num2'])) {
$num1 = $_GET['num1'];
$num2 = $_GET['num2'];
$sum = $num1 + $num2;
echo $num1 . " + " . $num2 . " = " . $sum;
}
?>
</body>
</html>
Account
