What are some best practices for sanitizing and displaying user input in PHP?

When displaying user input in PHP, it is important to sanitize the input to prevent potential security vulnerabilities such as cross-site scripting (XSS) attacks. One common method to sanitize user input is to use the htmlspecialchars() function to convert special characters to HTML entities. Additionally, it is good practice to validate user input before displaying it to ensure it meets the expected format.

// Sanitize and display user input
$userInput = "<script>alert('XSS attack!')</script>";
$cleanInput = htmlspecialchars($userInput, ENT_QUOTES, 'UTF-8');
echo $cleanInput;