<?php

    if(isset($_POST['submit'])) {
        $total = 0;

        if($_POST['operasi'] == "*" || $_POST['oprasi'] == "/") {
            $total = 1;
        }

        $total_field_diisi = 0;
        $operasi = $_POST['operasi'];
        foreach($_POST['input'] as $input) {
            if(isset($input['check'])) {
                if($operasi == "+") {
                    $total += $input['number'];
                } else if($operasi == "-") {
                    $total -= $input['number'];
                } else if($operasi == "/") {
                    $total /= $input['number'];
                } else if($operasi == "*") {
                    $total *= $input['number'];
                } else {
                    $total = false;
                    break;
                }
                $total_field_diisi ++;
            }
        }

        if($total_field_diisi <= 1) {
            $total = false;
        }



    }

?>


<form action="" method="post">
    <div class="form-group">
        <input type="number" name="input[0][number]" placeholder="Number 1" id=""> <input type="checkbox" name="input[0][check]" id="">
        <input type="number" name="input[1][number]" placeholder="Number 2" id=""> <input type="checkbox" name="input[1][check]" id="">
        <input type="number" name="input[2][number]" placeholder="Number 3" id=""> <input type="checkbox" name="input[2][check]" id="">
        <input type="text" name="operasi" id="" placeholder="operasi (+,-,/,*)">
        <br>
        <?php

            if(isset($total)) {
                if(!$total) {
                    echo "Error";
                } else {
                    echo "Total: " . $total . "<br/>";
                }
            }

        ?>
        <button type="submit" name="submit">Kirim</button>
    </div>
</form>