What are some best practices for organizing PHP scripts with multiple include statements for calculations?

When organizing PHP scripts with multiple include statements for calculations, it is best practice to create separate files for each calculation or related set of calculations. This helps to keep your code modular and easier to maintain. You can then include these files in your main script as needed to perform the calculations.

```php
// main_script.php

include 'calculation1.php';
include 'calculation2.php';
include 'calculation3.php';

// Perform calculations using functions or variables from included files
$result1 = calculate1();
$result2 = calculate2();
$result3 = calculate3();

// Output results
echo $result1;
echo $result2;
echo $result3;
```
In this example, we have a main script that includes separate files for three different calculations. Each included file contains functions or variables related to that specific calculation. This approach keeps the code organized and makes it easier to manage and update individual calculations.