How can the issue of variable passing between HTML forms and PHP scripts be effectively addressed to ensure data integrity?

Issue: To ensure data integrity when passing variables between HTML forms and PHP scripts, it is essential to properly sanitize and validate user input to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. One effective way to address this issue is to use PHP functions like htmlspecialchars() and filter_input() to sanitize input data before processing it in the PHP script.

// Example of sanitizing user input from an HTML form
$user_input = $_POST['user_input'];
$clean_input = htmlspecialchars($user_input);