What best practices should be followed when modifying HTMLArea editor in a PHP project?

When modifying the HTMLArea editor in a PHP project, it is important to follow best practices to ensure the editor functions correctly and securely. This includes properly sanitizing user input to prevent cross-site scripting attacks, implementing CSRF protection to prevent unauthorized form submissions, and validating user input to ensure it meets the required format.

// Example of sanitizing user input before displaying it in the HTMLArea editor
$user_input = $_POST['user_input'];
$clean_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');
echo '<textarea id="editor">' . $clean_input . '</textarea>';