<?php

if (isset($_POST['ok'])) {

$a = isset($_POST['a']) ? abs($_POST['a']) : false;

$b = isset($_POST['b']) ? abs($_POST['b']) : false;



echo 'Natija:' . $a + $b;

}

?>



<form method="post">

<input type="text"  name="a"><br>

<input type="text" name="b"><br>

<input type="submit" name="ok" value="Qo'shish">

</form>