[Joomla] Problem when calling this function

Hello;

I have a portion of code that work outside a function, but when i include it inside a function it didn't work. I don't know why?

Certainly i am missing something but i could see it. If someone saw the error so please please let me correct it.

Thank you for your help.

This is the source code of the file:

<?php
define('_JEXEC', 1);
define('JPATH_BASE', realpath(dirname(__FILE__)));
require_once(JPATH_BASE.'/includes/defines.php');
require_once(JPATH_BASE.'/includes/framework.php');
require_once(JPATH_BASE.'/libraries/joomla/factory.php');


$article_life   	= 72;	// Article lifetime in hours, 72 hours = 3 days
$articles_number  	= 15; 	// Alowed number of articles inside a category

$db     = JFactory::getDBO();
$query  = $db->getQuery(true);

Cleanup(49, 48, 0);

function Cleanup($catid, $life = $article_life, $number = $article_number){

	// Request articles in the category from database
	$query	->select("*")
		->from("#__content")
		->where("catid = " . $catid);
	$db	->setQuery($query);
	$articles	= $db->loadObjectList();
	$nbr = count($articles);
	if($nbr <= $number)
		return;
	foreach($articles as $article) { // loop through articles
		// $article->created looks like 2012-12-10 16:53:15
		$date_created = DateTime::createFromFormat('Y-m-d H:i:s', $article->created);
		$timestamp_created = $date_created->format('U');
		$diff_s = time() - $timestamp_created;
		$diff_h = $diff_s / 3600;
		if($diff_h > $life) { // If article life is bigger than the allowed value, remove it!
			$query = "DELETE from #__content where id = " . $article->id;
		        $db     ->setQuery($query);
		        $db     ->query();
		}
	} // End foreach
	return;
} // End Cleanup

?>