What are the best practices for structuring PHP files to make them easily includable and navigable to specific sections?

When structuring PHP files to make them easily includable and navigable to specific sections, it is recommended to organize the code into functions or classes and use include or require statements to include them in other files. Additionally, using comments and clear naming conventions can help developers easily navigate through the codebase.

// Example of structuring PHP files for easy inclusion and navigation

// functions.php
function calculateSum($a, $b) {
    return $a + $b;
}

// include functions.php in another file
require_once 'functions.php';

// index.php
echo calculateSum(5, 3);