Are there any best practices for handling and sanitizing user input containing HTML in PHP?

When handling user input containing HTML in PHP, it is important to sanitize the input to prevent XSS attacks and other security vulnerabilities. One common approach is to use the `htmlspecialchars()` function to encode HTML special characters before outputting the input to the browser. This function will convert characters like `<` and `>` into their HTML entity equivalents, preventing them from being interpreted as HTML tags.

// Sanitize user input containing HTML
$user_input = '<script>alert("XSS attack!")</script>';
$sanitized_input = htmlspecialchars($user_input);

// Output sanitized input
echo $sanitized_input;