how to parse php code stored in databases?

Hi there, I thought it would be a great idea to store the code of nearly all my web pages in "text" fields of a mysql database. Now I've got the problem that I want to use php in those pages. Let's say $row["content"] contains the string "<? echo 'Hello World!' ?>". Then echo $row["content"] only produces the unparsed <? echo 'Hello World!' ?> which effectivly displays nothing, because the browser doesn't know the "<?" tag. How can I tell PHP to parse this string before displaying it??? Thanks for any suggestions...