What are some common pitfalls to avoid when integrating PHP and HTML code?

One common pitfall to avoid when integrating PHP and HTML code is mixing PHP and HTML code within the same file without proper separation. This can lead to messy and hard-to-maintain code. To solve this, it's recommended to use a template engine like Twig or Blade to separate the PHP logic from the HTML presentation.

<?php
// Using Twig template engine
require_once 'vendor/autoload.php';

$loader = new \Twig\Loader\FilesystemLoader('templates');
$twig = new \Twig\Environment($loader);

echo $twig->render('index.html', ['variable' => $value]);
?>