embedding PHP in MySQL

I've been working on this for a few days and can't get it. I would like to stick some php code into a sql databases and be able to evaluate it when it's called up. Foe example, let's say there's some text in a table in MySql that says "blah blah blah <? $mysql_query("SELECT * FROM X WHERE 1); $someothercode; ?> blah blah blah blah blah". I wan the end, displaying result to be: "blah blah blah {executed php code} blah blah blah blah". Now, I know that eval() is involved, but I don't want it accidentally executing code outside the "<? ?>" so I need a way to pluck out bits of code, evaluate them, and put them back in. Any ideas? Thanks, Michael