What best practices should be followed when updating PHP scripts to ensure compatibility with different PHP versions and avoid security vulnerabilities?

When updating PHP scripts, it is important to follow best practices to ensure compatibility with different PHP versions and avoid security vulnerabilities. This includes using the latest PHP version, using secure coding practices, avoiding deprecated features, and regularly updating libraries and dependencies.

// Example of using secure coding practices by sanitizing user input
$user_input = $_POST['user_input'];
$clean_input = filter_var($user_input, FILTER_SANITIZE_STRING);