Smart code for setting php memory_limit in settings.php

This smart wordpress code would be useful to Drupal:

if ( !defined('WP_MEMORY_LIMIT') )
	define('WP_MEMORY_LIMIT', '32M');

if ( function_exists('memory_get_usage') && ( (int) @ini_get('memory_limit') < abs(intval(WP_MEMORY_LIMIT)) ) )
	@ini_set('memory_limit', WP_MEMORY_LIMIT); 

If it isn't set, it sets it to 32M. If it is set, it checks to see if the current usage (limit) is greater than 32 (in which case it leaves things alone). I'm not sure why they call function_exists('memory_get_usage'): http://de.php.net/manual/en/function.memory-get-usage.php