What are common pitfalls when including JavaScript in PHP files?

Common pitfalls when including JavaScript in PHP files include not properly escaping characters, mixing PHP and JavaScript syntax incorrectly, and not separating PHP and JavaScript code effectively. To avoid these pitfalls, use PHP to echo JavaScript code within script tags and ensure that any PHP variables or data being passed into the JavaScript code are properly escaped.

<?php
// Example of including JavaScript in a PHP file without common pitfalls

// PHP code to retrieve data
$data = "Hello, world!";

// Echoing JavaScript code within script tags
echo '<script>';
echo 'var message = "' . htmlspecialchars($data) . '";'; // Escaping PHP variable data
echo 'console.log(message);';
echo '</script>';
?>