<?php

    /*
     * Add
     */
    if(isset($_POST['add'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if(is_numeric($x) && is_numeric($y)) {
            $answer = $x + $y;
        } else {
            $answer = "Error";
        }
    }

    /*
     * Subtract
     */
    if(isset($_POST['subtract'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if(is_numeric($x) && is_numeric($y)) {
            echo $x + $y;
            $answer = $x - $y;
        } else {
            $answer = "Error";
        }
    }

    /*
     * Multiply
     */
    if(isset($_POST['multiply'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if(is_numeric($x) && is_numeric($y)) {
            $answer = $x * $y;
        } else {
            $answer = "Error";
        }
    }

    /*
     * Divide
     */
    if(isset($_POST['divide'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if($y == 0) {
            $answer = "INF";
        } else if(is_numeric($x) && is_numeric($y)) {
            $answer = $x / $y;
        } else {
            $answer = "Error";
        }
    }

    /*
     * Square
     */
    if(isset($_POST['square'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if(is_numeric($x)) {
            $answer = pow($x, 2);
        } else {
            $answer = "Error";
        }
    }

    /*
     * Power
     */
    if(isset($_POST['power'])) {
        $x = $_POST['x'];
        $y = $_POST['y'];

        if(is_numeric($x) && is_numeric($y)) {
            $answer = pow($x, $y);
        } else {
            $answer = "Error";
        }
    }

    /*
     * Root
     */
    if(isset($_POST['root'])) {
        $x = $_POST['x'];
        // $y = $_POST['y'];

        if(is_numeric($x)) {
            $answer = sqrt($x);
        } else {
            $answer = "Error";
        }
    }

    /*
     * Table
     */
     if(isset($_POST['table'])) {
         $x = $_POST['x'];
         $y = $_POST['y'];

         $tafel = array();

         for($i = 1 ; $i < 11 ; $i++) {
             $aq =  $x * $i;
             $tafel[]+=$aq;

         }

         $answer = implode(', ', $tafel);
     }

?>