Dynamically replace text before output

Does anyone know of a way to replace text in web pages, dynamically, before they are returned to the client?

For example, replace all occurances of a company name with a link to that companies page?

Ideally, the solution would work with any HTTP text, not just from PHP.

Any suggestions?

Thanks.

Well you can READ the pages in with a PHP script and the fopen() function. Read it all in into a string and do a ereg_replace("whatever","withsomething",$string) or str_replace() afterwards. This should help ... then you can simply echo $string; and the page is displayed the way u want it.