PHP to do simple calculator

Use php to do simple calculator
It can be +, -, *, / operations.
As shown below
<?php 
    if (isset($_POST['button'])) {
        $num1 = $_POST['num1'];
        $num2 = $_POST['num2'];
        $op = $_POST['op'];
        switch ($_POST['op']) {
            case '+':    
                $result = $num1 + $num2;
                break;
            case '-':    
                $result = $num1 - $num2;
                break;
            case '*':    
                $result = $num1 * $num2;
                break;
            case '/':    
                $result = $num1 / $num2;
                break;
        }
        echo <<<str
        <script type="text/javascript">
             window.onload=function(){
                 document.getElementById('num1').value = '$num1';
                 document.getElementById('op').value = '$op';
                 document.getElementById('num2').value = '$num2';
             document.getElementById('result').value = '$result';
     }
     </script>
str;
    }

 ?>

<body>
<form method="post" action="">
    <input type="text" name="num1" id="num1">
    <select name="op" id="op">
        <option value="+">+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
    </select>
    <input type="text" name="num2" id="num2">
    <input type="submit" name="button" value="=">
    <input type="text" name="result" id="result">
</form>
</body>
PHP to do simple calculator

Guess you like
