What are some common functions in PHP that can help maintain formatting, such as nl2br, stripslashes, and htmlentities?

When dealing with user input in PHP, it's important to maintain formatting and prevent security vulnerabilities. Functions like nl2br, stripslashes, and htmlentities can help with this. nl2br converts newlines to <br> tags, stripslashes removes backslashes, and htmlentities converts special characters to HTML entities to prevent XSS attacks.

// Example usage of nl2br, stripslashes, and htmlentities
$userInput = $_POST['user_input'];

// Apply necessary formatting functions
$formattedInput = nl2br(stripslashes(htmlentities($userInput)));

echo $formattedInput;