Calculate a php class with a new variable

Question

I am not sure what a class is. i have a page already written that has classes in place for equations. I have made some new variables for some new equation but am getting incorrect results, I basically need to multiple / divide / subtract these prebuilt classes against my new variable
this is what i have so far
<?php
                                $utilityHost = 21.0;
                                $col4 = $option_two->amount_due_before - $option_two->four_weeks_security - $option_two->fee;
                                $col5 = $col4 / $row_Recordset1['rental_price'];
                                $col3 = $utilityHost * $col5;
                                $col6 = $row_Recordset1['rental_price'] * $col5;
                                ?>
$col4 is the variable using the pre built classes.
all of these are being echoed out into a table
e.g
<?php
echo "£" . number_format($row_Recordset1['rental_price'] - $utilityHost);
?>
<?php
echo "£" . $utilityHost;
?>
the classes
<?php
require_once('../lib/PaymentOptionOne.php');
                        require_once('../lib/PaymentOptionTwo.php');
                        require_once('../lib/PaymentOptionThree.php');
                        require_once('../lib/PaymentOptionFour.php');
     $rent = $row_Recordset1['rental_price'];
                        if($row_Recordset1['weekly_rate'] != 0.00)
                            $rent = $row_Recordset1['weekly_rate'];
                        $weeks = $row_Recordset1['weeks'] / 7;
                                                            $query = "SELECT * FROM editprop WHERE prop_id = %s";
                                                            $query = sprintf($query, GetSQLValueString($row_Recordset1['prop_id'], "text"));
                                                            $results = mysql_query($query);
                                                            while($row = mysql_fetch_array($results))
                                                                      $option_three_rent = $row['rental_price_monthly'];
                                                                      if(empty($option_three_rent))
                                                                                $option_three_rent = $rent;
                        $option_one = new PaymentOptionOne($rent, $weeks);
                        $option_two = new PaymentOptionTwo($rent, $weeks);
                        $option_three = new PaymentOptionThree($option_three_rent, $weeks);
thanks in advance

Answer 1

>multiple my variable with the classes that are already in place
Classes are complex constructs that hold data structures and methods. You don't multiple a variable with a class - you can reference a variable within that class or object. What exactly is the problem you are having with this?
This syntax should work (note that I'm just using arbitrary variables:
$col4 = $option_two->amount_due_before * $col2
I think it is critical that you become familiar with object oriented coding if you are going to be working with it.
http://www.elated.com/articles/object-oriented-php-for-absolute-beginners/