A simple little application for php to calculate things.

Code:
<?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); 
     } 
} 
?>