Code Question

[wraggster]

Hi all i have some code i want to insert into my forum ie this

function convert_aff_links( $_body, $_aff_id = '2pz' )
{
	$_body = preg_replace
	(
		'@://(w+\.)?(playasia|play-asia)\.com/?([^/a-zA-Z])@',
		'://www.play-asia.com/SOap-23-' . '83-' . $_aff_id . '-50-00.html$3',
		$_body
	);

	$_body = preg_replace
	(
		'/paOS-(\d{2})/',
		'SOap-23-' . '83-' . $_aff_id . '-50-$1',
		$_body
	);

	return $_body;
}

but when i edit the header/footer templates it shows up on my forum rather than just hidden in the background, is there a bit of code i need to add to make it hide ?