What are the differences between server-side and client-side methods for opening new windows in PHP?

Server-side methods for opening new windows in PHP involve using PHP code to generate HTML links or buttons that have a target attribute set to "_blank" to open a new window. Client-side methods involve using JavaScript to open a new window when a user interacts with a button or link. PHP code snippet for server-side method:

<a href="newpage.php" target="_blank">Open New Window</a>
```

PHP code snippet for client-side method:
```php
<button onclick="window.open('newpage.php', '_blank')">Open New Window</button>