What are the potential pitfalls of mixing PHP and HTML for styling database query results?

Mixing PHP and HTML for styling database query results can lead to messy and hard-to-maintain code. To solve this issue, it's recommended to separate the PHP logic from the HTML markup by using a templating system like PHP's built-in `include` function or a more robust templating engine like Twig.

```php
<?php
// Fetch data from database
$query = "SELECT * FROM table";
$result = mysqli_query($connection, $query);

// Store results in an array
$data = [];
while ($row = mysqli_fetch_assoc($result)) {
    $data[] = $row;
}

// Include a separate template file for displaying the results
include 'template.php';
?>
```

In the `template.php` file, you can format and style the database query results using HTML and CSS without mixing it with PHP logic. This separation makes the code cleaner and easier to manage.