Adverts in Articles

[Napoleon001 0]

Hi,

You know how some websites have a page of text and somehow in various places they put related adverts in it?
A bit like this tiny example:

[!--quoteo--][div class=\'quotetop\']QUOTE[/div][div class=\'quotemain\'][!--quotec--]This is a 1st paragraphe of text

SOME FANCY AND ANNOYING ADVERT THAT DISTRACTS YOU FROM ARTICLE

This is another paragraphe[/quote]
How do they do it?

Is there a better way of doing it than using "ereg_replace" like this? (wouldn't it be great if one could put PHP scripts into a DB)

[code]//I get my normal text from db
$textfromdb="<p>This is a 1st paragraphe of text</p><p>This is another paragraphe</p>";
// search for paragraphe break
$searchtext="</p><p>"; //could be a specially inserted tag
//get my advert from db
$some_advert = "<img src="image.gif">"; //This would also come from a db
//do search and replace
$bodytext = ereg_replace ($textfromdb, $searchtext, $some_advert);
//output result
echo $bodytext;[/code]
Any suggestions?

By the way, I'm not using it for putting annoying adverts into text, I hate that but its a good example that we're all subject to, so easy to visualise.
I have a need to put dynamic stuff in the contents that comes out of a DB (from 1 table cell) such as display 1 client testimonial randomly selected from a list or a randomly selected illustration picked from a selection, examples go on...

Any suggestions how to do this a better way? Maybe some techique or function that I've never heard of...
... much appreciated!