What are some best practices for organizing PHP code to avoid header modification errors?

When organizing PHP code to avoid header modification errors, it is best practice to ensure that no output is sent to the browser before calling the header() function. This includes any whitespace or HTML tags before the opening <?php tag. To prevent header modification errors, make sure to place all header-related code at the beginning of your PHP files before any other code or output.

<?php
// Correct way to set headers at the beginning of a PHP file
header("Content-Type: text/html");

// Other PHP code can follow here
echo "Hello, World!";