Pulling text from a database that calls a variable inside <?php ?>

[ShepMode]

This is the text I pull from the database:

Some text here <?php print $_POST["variable"]; ?>, some more text here.

Unfortunately because I am outputting the value using <?php print mysql_result($main,0,"body"); ?> the php command within that value is not recogised. How do I make sure it is?

[superwormy]

eval() www.php.net/eval

$code_and_html = " <b> <?php print (10 * 10); ?> </b> ";

eval (" ?> " . $code_and_html . " <?php ");