Are there any security concerns to consider when using PHP to handle client-side interactions with JavaScript?

One security concern to consider when using PHP to handle client-side interactions with JavaScript is the risk of Cross-Site Scripting (XSS) attacks. To prevent XSS attacks, it is important to properly sanitize and validate user input before processing it in PHP.

// Sanitize user input before processing
$user_input = htmlspecialchars($_POST['user_input'], ENT_QUOTES);