Server side code, on the other hand, is never seen by the browser. The browser is not and should never need to be aware of server side scripts such as PHP. While a web page consists of client side code, this code is often either partially or entirely generated by a server side script. For example:
$title = 'Client Side Vs. Server Side Code'; if($title == '') echo '<title>Tinsology</title>'; else echo "<title>$title</title>";
When you navigate to a page containing the code above the browser will see “<title>Client Side Vs. Server Side Code</title>”. That’s it. The browser does not see any of the PHP code that generated the title. When you request a page containing PHP code from the server, the server first processes that page and then sends the resulting output to the client.
Server side code is browser independent (unless explicitly coded otherwise). This means that if the page you create looks different in Internet Explorer than it does in Opera it has nothing to do with your PHP code, but rather the resulting client side code.