How can I prevent HTML content from being included in a variable in PHP?

To prevent HTML content from being included in a variable in PHP, you can use the `htmlspecialchars()` function to escape any HTML characters. This function converts special characters like `<`, `>`, `&`, and `"` to their HTML entities, preventing them from being interpreted as HTML tags. By using `htmlspecialchars()` on user input or any content that may contain HTML, you can ensure that it is safely stored in a variable without any risk of executing HTML code.

// Example code snippet to prevent HTML content from being included in a variable
$user_input = "<script>alert('Hello!');</script>"; // User input containing HTML tags
$safe_input = htmlspecialchars($user_input); // Escaping HTML characters
echo $safe_input; // Output: <script>alert('Hello!');</script>