PHP - simple calculator

Buat 1 funtion :

<?php
// Defining the "calc" class
class calc {
var $number1;
var $number2;
function add($number1,$number2)
{
$result =$number1 + $number2;
echo "The sum of $number1 and $number2 is $result<br><br>";
echo "$number1 + $number2 = $result";
exit;
}
function subtract($number1,$number2)
{
$result =$number1 - $number2;
echo "The difference of $number1 and $number2 is $result<br><br>";
echo "$number1 &#045 $number2 = $result";
exit;
}
function divide($number1,$number2)
{
$result =$number1 / $number2;
echo "$number1 divided by $number2 is $result<br><br>";
echo "$number1 ? $number2 = $result";
exit;
}
function multiply($number1,$number2)
{
$result =$number1 * $number2;
echo "The product of $number1 and $number2 is $result<br><br>";
echo "$number1 x $number2 = $result";
exit;
}
function square($number)
{
$result = $number * $number;
echo "The square of $number is $result<br><br>";
echo "$number &#94; 2 = $result";
}
function squareroot($number)
{
$result = sqrt($number);
echo "The square root of $number is $result<br><br>";
}
function cube($number)
{
$result = $number * $number * $number;
echo "The cube of $number is $result<br><br>";
echo "$number1 &#94; 3 = $result";
}
}
//Creating object of class
$calc = new calc();
?>

Kemudian buat 1 form bersama php untuk calculator tersebut

<title>PHP Calculator </title>
<h2>Calculator 1</h2>
<form name="calc" action="" method="POST">
Number 1: <input type="text" name="value1"><br>
Number 2: <input type="text" name="value2"><br>
Operation:
<select name="oper">
<option value="add">Addition</option>
<option value="subtract">Subtraction</option>
<option value="divide">Division</option>
<option value="multiply">Multiplication</option>
</select>
<br>
<input type="submit" value="Calculate" name="submit">
</form>
<br>
<br>
<h2>Calculator 2</h2>
<form name="calc2" action="" method="POST">
Number : <input type="text" name="value"><br>
Operation:
<select name="operat">
<option value="square">Square</option>
<option value="squareroot">Square Root</option>
<option value="Cube">Cube</option>
</select>
<br>
<input type="submit" value="Calculate" name="submit1">
</form>

<?php
if($_POST['submit']){
$number1 = $_POST['value1'];
$number2 = $_POST['value2'];
$oper = $_POST['oper'];
if(!$number1){
echo "<font color='red'>Please enter first number in calculator 1</font>";
exit;
}
if(!$number2){
echo "<font color='red'>Please enter second number in calculator 1</font>";
exit;
}
if(!$oper){
echo "<font color='red'>Please select operator in calculator 1</font>";
exit;
}
if(!eregi("[0-9]", $number1)){
echo "<font color='red'>First number must be digits in calculator 1</font>";
exit;
}
if(!eregi("[0-9]", $number2)){
echo "<font color='red'>Second number must be digit in calculator 1</font>";
exit;
}
if($oper == "add"){
$calc->add($number1,$number2);
}
if($oper == "subtract"){
$calc->subtract($number1,$number2);
}
if($oper == "divide"){
$calc->divide($number1,$number2);
}
if($oper == "multiply"){
$calc->multiply($number1,$number2);
}
}
?>
<?php
if($_POST['submit1']){
$number = $_POST['value'];
$operat = $_POST['operat'];
if(!$number){
echo "<font color='red'>Please enter number in calculator 2</font>";
exit;
}
if(!$operat){
echo "<font color='red'>Please select operator in calculator 2</font>";
exit;
}
if(!eregi("[0-9]", $number)){
echo "<font color='red'>Value must be digits in calculator 2</font>";
exit;
}
if($operat == "square"){
$calc->square($number);
}
if($operat == "cube"){
$calc->cube($number);
}
if($operat == "squareroot"){
$calc->squareroot($number);
}
}
?>