What are the best practices for handling user input in PHP scripts to prevent issues with URL encoding?

When handling user input in PHP scripts, it is important to properly handle URL encoding to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. One way to mitigate these risks is by using functions like `htmlspecialchars()` and `urlencode()` to sanitize and encode user input before using it in your scripts.

// Example of handling user input with proper URL encoding
$userInput = $_GET['user_input'] ?? ''; // Retrieve user input from GET request
$sanitizedInput = htmlspecialchars(urlencode($userInput)); // Sanitize and encode user input
echo $sanitizedInput; // Output the sanitized and encoded user input