Plan your formula from the scratch
We recommend you to make tests in excel, Google Docs/Drive or other spreadsheet program.
Write it in simple terms like (A + B) * C, nobody like you knows how your business works.
Add required options in OpenCart, selecting where to use a combo, radio, checkbox or a textbox.

Formulas can be written in several lines for better reading
Remember that CFO uses PHP so take care of the syntax and end each line with “;”

```\$FinalPrice = ({1V} + {2V}) * \$Price;
\$FinalPrice = \$FinalPrice + {3P} + {4P};
```

If you are using your own variables take care not using reserverd words, the better way to avoid it is to use a prefix like “\$my”, for example “\$myTest”.
PHP is case sensitive for variables, functions, etc…

```\$myTest = ({1V} + {2V}) * \$Price;
\$myTest = \$myTest+ {3P} + {4P};
\$FinalPrice = \$myTest;
```

```// Width and Height are expressed in meters for this calculation
\$myTest = ({1V} + {2V}) * \$Price;
\$myTest = \$myTest+ {3P} + {4P};

// Here we have the final price
\$FinalPrice = \$myTest;
```

Of course you can use conditionals

```// First calculate square meters (Width x Height in our example)
\$SquareMeters = {1V} * {2V};

// Use some tmp variable for a hypothetical extra cost
\$ExtraCost = 0;
if(\$SquareMeters>10) {
// Oh it's really big, this will add \$5 to the final price
\$ExtraCost = 5;
}

\$FinalPrice = (\$SquareMeters * \$Price) + \$ExtraCost;
```