How can the issue of user input manipulation through GET requests be addressed in PHP scripts?

User input manipulation through GET requests can be addressed by validating and sanitizing all input data before using it in the PHP script. This can prevent malicious users from injecting harmful code or manipulating data. One way to achieve this is by using PHP functions like `filter_input()` or `htmlspecialchars()` to sanitize input data.

// Validate and sanitize input data from GET request
$user_input = filter_input(INPUT_GET, 'user_input', FILTER_SANITIZE_STRING);

// Use the sanitized input data in the script
echo "User input: " . $user_input;