What are the common pitfalls when integrating WordPress with external HTML pages in PHP, and how can they be resolved?

Common pitfalls when integrating WordPress with external HTML pages in PHP include issues with conflicting stylesheets, JavaScript conflicts, and problems with accessing WordPress functions. These can be resolved by properly enqueueing stylesheets and scripts, using WordPress functions to include header and footer files, and ensuring that the necessary WordPress functions are available in the external HTML pages.

<?php
// Include WordPress functions
require_once('wp-load.php');

// Include WordPress header
get_header();

// Your external HTML content here

// Include WordPress footer
get_footer();
?>