How important is structured programming in PHP development, and how does it relate to using functions and includes?

Structured programming is essential in PHP development as it helps organize code into logical structures, making it easier to read, debug, and maintain. Using functions allows for code reusability and modularity, while includes help in separating code into different files for better organization.

<?php
// Example of structured programming using functions and includes

// Include the file containing functions
include 'functions.php';

// Call a function to perform a specific task
$result = calculate(10, 5);

echo $result;

?>