How to prevent XSS with HTML PHP

Question

How do I prevent XSS (cross-site scripting) using just HTML and PHP?

Answer 1

Hello,

HTML Encoding

htmlspecialchars will convert any "HTML special characters" into their HTML encodings, meaning they will then not be processed as standard HTML. To fix our previous example using this method:

<?php
echo '<div>' . htmlspecialchars($_GET['input']) . '</div>';
// or
echo '<div>' . filter_input(INPUT_GET, 'input', FILTER_SANITIZE_SPECIAL_CHARS) . '</div>';

Would output:

<div>&lt;script src=&quot;http://example.com/runme.js&quot;&gt;&lt;/script&gt;</div>

Everything inside the <div> tag will not be interpreted as a JavaScript tag by the browser, but instead as a simple text node. The user will safely see:

<script src="http://example.com/runme.js"></script>

Thank you!!