In what situations should PHP developers consider using separate functions or classes for unit conversion logic to improve code readability and maintainability?

When dealing with unit conversion logic in PHP, developers should consider using separate functions or classes to improve code readability and maintainability. By encapsulating the conversion logic in separate functions or classes, developers can easily reuse the code, make it more modular, and enhance the overall readability of the codebase. This approach also allows for easier testing and debugging of the conversion logic.

<?php

// Function for converting temperature from Celsius to Fahrenheit
function celsiusToFahrenheit($celsius) {
    return ($celsius * 9/5) + 32;
}

// Function for converting temperature from Fahrenheit to Celsius
function fahrenheitToCelsius($fahrenheit) {
    return ($fahrenheit - 32) * 5/9;
}

// Example of using the conversion functions
$celsiusTemp = 25;
$fahrenheitTemp = celsiusToFahrenheit($celsiusTemp);
echo "{$celsiusTemp} degrees Celsius is equal to {$fahrenheitTemp} degrees Fahrenheit.";

?>