alert messages!

i tried creating alert messages using php but i just couldnt find any method to do so,so i used the javascript alert().will i be penalised for this becouse this is just an add on,not a required function?if there is a way i can do this in php,then what is it?

I think you need to revise exactly how PHP and JavaScript operate.

PHP is fully interpreted on the server, and no PHP is served to the users browser. It cannot therefore respond to user input in real time. (Server-side)
It is a preprocessor, and only operates before the page is served.

JavaScript is interpreted by the users browser, and can therefore respond to user input / alerts. (Client-side)

Have a look here -

http://html.net/tutorials/php/lesson1.php

http://www.w3schoolas.com/history%20of%20php.php