How can PHP developers validate and sanitize user input to prevent cross-site scripting (XSS) vulnerabilities?

To prevent cross-site scripting (XSS) vulnerabilities, PHP developers can validate and sanitize user input by using functions like htmlspecialchars() to escape special characters that could be used for malicious purposes. This ensures that any user input displayed on a webpage is properly encoded and does not execute any scripts.

// Validate and sanitize user input to prevent XSS vulnerabilities
$user_input = $_POST['user_input']; // Assuming user input is received via POST method

$clean_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');

// Use $clean_input in your application to display user input safely