Are there any common pitfalls to avoid when using PHP functions for data validation?

One common pitfall to avoid when using PHP functions for data validation is not properly sanitizing user input, which can leave your application vulnerable to SQL injection attacks. To solve this issue, always use functions like `mysqli_real_escape_string()` to escape user input before using it in database queries.

// Sanitize user input to prevent SQL injection
$user_input = mysqli_real_escape_string($db_connection, $_POST['user_input']);