What are the potential pitfalls of using special characters in HTML when working with PHP?

Special characters in HTML can cause issues when working with PHP, especially when handling user input. To avoid problems such as injection attacks or rendering errors, it is important to properly escape special characters before displaying them. One way to do this is by using the htmlspecialchars() function in PHP, which converts special characters to HTML entities, preventing them from being interpreted as code.

$user_input = "<script>alert('Hello');</script>";
$escaped_input = htmlspecialchars($user_input);
echo $escaped_input;