simple php calculator

   =

Php Code:


<?php
    
echo "<p>simple php calculator</p>";
    echo 
"<form action='' autocomplete='off' method='GET'>";
       
$mydefault="";
        if (isset(
$_GET["a"])) {
            echo 
"<input type='text' name='a' value='" $_GET["a"] . "'>";
            
$mydefault=$_GET["operator"];
        }
        else
            echo 
"<input type='text' name='a'>";
        echo 
"<select name='operator'>
                    <option>+</option>
                    <option>-</option>
                    <option>*</option>
                    <option>/</option>
                    <option value=" 
$mydefault " selected>" $mydefault "</option></select>";
        if (isset(
$_GET["b"]))
            echo 
"<input type='text' name='b' value='" $_GET["b"] . "'>";
        else
            echo 
"<input type='text' name='b'>";
        echo 
"=";
        if (isset(
$_GET["a"])) {
                
$a=(int)$_GET["a"];
                
$b=(int)$_GET["b"];
                
$operator=$_GET["operator"];
                switch (
$operator) {
                        case 
"+":
                            echo 
$res=$a+$b
                            break;
                        case 
"-":
                            echo 
$res=$a-$b
                            break;
                        case 
"*":
                            echo 
$res=$a*$b
                            break;
                        case 
"/":
                            if (
$b 0)
                                echo 
$res=$a/$b
                            break;
                    }
            }
        echo 
"<br><br>";
        echo 
"<input type='submit' value='Calculate'>";
    echo 
"</form>";
?>