Simple Calculator in PHP (OOP principles)

#php #oop #html

So lets build a calculator which does the following.
1) Addition
2) Multiplication
3) Division
4) Subtraction

The folder and file structure is given below

Lets get the html index.php sorted first, so whats in it?

<?php

 include 'includes/class-autoload.inc.php';
?>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>

<form action="includes/calc.inc.php" method = "post">

    <p>Calculator V01</p>
    <input type= "number" name="num1" placeholder="First number">
    <select name="oper" >
      <option value="add"> Addition </option>
      <option value="sub"> Substraction </option>
      <option value="div">Division </option>
      <option value="mul">Multiplication </option>
    </select>
    <input type="number" name="num2" placeholder="Second number">
    <button type="submit" name="submit">  Calculate</button>

</form>

</body>
</html>

The code above should be self-explanatory, if you are unsure about the class-autoload.php file have a look at this article(
https://dev.to/naveenkolambage/autoload-classes-in-php-4474 ) about it.

And here is the code we have in class-autoload.inc.php

<?php

spl_autoload_register('myAutoLoader');

function myAutoLoader($className){
    $url= $_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];

    if(strpos($url, 'includes')!==false){
        $path = '../classes/';
    }
    else{
        $path = 'classes/';
    }
    $extension = '.class.php';
    require_once $path.$className.$extension;
}

Then we look at the calculator class file which is calc.class.php

<?php

class Calc{
    public $operator;
    public $num1;
    public $num2;


    public function __construct(string $one, int $two, int $three){
        $this->operator = $one;
        $this->num1 = $two;
        $this->num2 = $three;
    }


    public function calculator(){
     switch ($this->operator) {
         case 'add':
            $result = $this->num1 + $this->num2;
            return $result;             
            break;
        case 'sub':
            $result = $this->num1 - $this->num2;
            return $result;             
            break;
        case 'div':    
             $result = $this->num1 / $this->num2;
             return $result;             
             break;
        case 'mul':    
             $result = $this->num1 * $this->num2;
             return $result;             
             break;

     }
    }

}

Then the next file is calc.inc.php

<?php
include 'class-autoload.inc.php';

$oper = $_POST["oper"];
$num1 = $_POST["num1"];
$num2 = $_POST["num2"];

$calc = new Calc($oper,$num1,$num2);

try {
    echo $calc->calculator();
} catch (TypeError $e) {
    echo "Error!: " .$e->getMessage();
}

?>

When we load this up on xampp we can see the following.