In the provided PHP code snippet, what are the common pitfalls or errors that could lead to unexpected behavior or lack of functionality?

One common pitfall in the provided PHP code snippet is the lack of error handling for database queries. If a query fails, it can lead to unexpected behavior or lack of functionality. To address this issue, you should always check the result of a query and handle any potential errors that may occur.

// Check if the query was successful before proceeding
if($result){
    // Process the query result
} else {
    // Handle the error, such as logging it or displaying a message to the user
}