What are some best practices for handling user input from a Textarea in PHP to prevent security vulnerabilities?

When handling user input from a Textarea in PHP, it is important to sanitize and validate the input to prevent security vulnerabilities such as SQL injection or cross-site scripting (XSS) attacks. One way to do this is by using the htmlspecialchars() function to encode special characters and prevent them from being interpreted as HTML or JavaScript code.

// Sanitize and validate user input from Textarea
$user_input = $_POST['textarea_input'];
$clean_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');