PHP Calculator

http://www.youtube.com/watch?v=luUXm2Bo3rQ
A simple little application for php to calculate things.

Code:

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<?php
// Define to make this all one document
$page = $_GET['page'];

// Defining the "calc" class
class calc {
    var $number1;
    var $number2;

                  //Create the function to add
          function add($number1,$number2)
          {
                  $result =$number1 + $number2;
                    echo("The sum of $number1 and $number2 is $result<br><br>");
                    echo("$number1 + $number2 = $result");
                    exit;
          }
                 
                  //Create the function to subtract
          function subtract($number1,$number2)
          {
                  $result =$number1 - $number2;
                    echo("The difference of $number1 and $number2 is $result<br><br>");
                    echo("$number1 &#045 $number2 = $result");
                    exit;
          }

                  //Create the function to divide
          function divide($number1,$number2)
          {
                  $result =$number1 / $number2;
                    echo("$number1 divided by $number2 is $result<br><br>");
                    echo("$number1 ÷ $number2 = $result");
                    exit;
          }

                  //Create the function to multiply
          function multiply($number1,$number2)
          {
                  $result =$number1 * $number2;
                    echo("The product of $number1 and $number2 is $result<br><br>");
                    echo("$number1 x $number2 = $result");
                    exit;
          }
}
//Make the functions easier to call
$calc = new calc();
?>
<TITLE>PHP Calculator</TITLE>
<form name="calc" action="?page=calc" method="POST">
Number 1: <input type=text name=value1><br>
Number 2: <input type=text name=value2><br>
Operation: <input type=radio name=oper value="add">Addition <input type=radio name=oper value="subtract">Subtraction <input type=radio name=oper value="divide">Division <input type=radio name=oper value="multiply">Multiplication</input><br>
<input type=submit value="Calculate">
</form>
<?php
//If the page has posted show results
if($page == "calc"){
$number1 = $_POST['value1'];
$number2 = $_POST['value2'];
$oper = $_POST['oper'];
    //This conditional checks to make sure numbers are entered
    if(!$number1){
          echo("You must enter number 1!");
          exit;
    }
    if(!$number2){
          echo("You must enter number 2!");
          exit;
    }
    //This conditional checks to make sure an operation is being ran
    if(!$oper){
          echo("You must select an operation to do with the numbers!");
          exit;
    }
        //Are only numbers being entered
    if(!eregi("[0-9]", $number1)){
          echo("Number 1 MUST be numbers!");
          exit;
    }
    if(!eregi("[0-9]", $number2)){
          echo("Number 2 MUST be numbers!");
          exit;
    }
        //Perform actions
    if($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);
    }
}
?>

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