Yes, To elaborate here:
PHP is *server side*, so it cant really do anything with the client!
You can however, with php, generate some content that is *client side*. That content is no longer php though.
Example:
You want to make some silly function, that every noob wants on his/her web-page, like maybe.. hmm.. let's say You want fading images!
You can then make php parse the javascript that fades the images, however it's the javascript that does the actual fading. (or, it's actually the browser, after a request from the javascript).
This is why it's not easy to make chat-clients, games, etc. that are not "tick based" in meerly php and html, as then you would have to refresh the web-page for any changes to be made.
One could however make it through flash, java or something like that, but then suddenly the users have to download additions to theire web-browser.
I however think that there is a line, let's say it goes like this:
No fancy effects [-----X---] All fancy effects
The X here, will vary based on what you want to present to your users.
If you want to have a gaming-site, I would say you could do maybe 80% flash-content.
If you are to have a site with meerly content, I would do max. 20% fancy content, but I would keep it as low as possible.
This X factor, will vary, based on what you have to present and how you can present it.
As for "embedding" files, you can make php attatch files through header(), but I for one, really hate those sites where you suddenly have music playing in the background.
Here too, the X-Factor comes into play! If it's a gaming site, for an action game, the background-sound might be cool in cooperation with some fancy flash-animations.
However, if you go to google to search, you dont want to hear music playing in the background.
Keep those background-attatchments where you have the "site in progress" animated gif's. (in your friends first webpage)
Olav Alexander Mjelde
Admin & Webmaster