sai che cambiando il codice nn cambia assolutamente nulla?

codice:
<h2>Simple</h2>
<form action="<?php $_SERVER['PHP_SELF'] ?>" method="post">
<input name="first" type="text" size="6" maxlength="10">
<select name="method1">
	<option value="add" selected>Add</option>
	<option value="sub">Subtract</option>
	<option value="multi">Multiply</option>
	<option value="div">Divide</option>
</select>
<input name="second" type="text" size="6" maxlength="10">



<input name="submit1" type="submit" value="Calculate">
</form>
<?php
// Simple
if ($submit1 == true) {
	if ($_POST['method1'] == "add") {$ans = $first + $second;}
	else if ($_POST['method1'] == "sub") {$ans = $first - $second;}
	else if ($_POST['method1'] == "multi") {$ans = $first * $second;}
	else if ($_POST['method1'] == "div") {$ans = $first / $second;}

$ans = number_format($ans, 2, ',', ' ');
echo "

The answer is $ans</p>";
}
?>