How can HTML validation tools help improve PHP code quality?

HTML validation tools can help improve PHP code quality by ensuring that the PHP code generates valid HTML output. This can help catch syntax errors, missing tags, or other issues that may not be immediately obvious when reviewing the PHP code alone. By using HTML validation tools, developers can ensure that the PHP code is generating correct and well-formed HTML, leading to better overall code quality.

<?php
// PHP code generating HTML output
$html = "<div><p>Hello, world!</div>"; // Missing closing </p> tag

// Output the HTML
echo $html;
?>