How to NULL an array?

I have a from and I want parts of it not to display. Do I nullify the parts of the array I dont want to show or just delete? And if its best to null..how do I do that? I dont want the duration to show.

$wpdb->update( $wpdb->jr_job_packs, array(
				'pack_name' 			=> $posted['pack_name'],
				'pack_description' 		=> $posted['pack_description'],
				'pack_duration' 		=> $posted['pack_duration'],
				'pack_cost' 			=> $posted['pack_cost'],
				'job_count' 			=> $posted['job_count'],
				'job_duration'			=> $posted['job_duration'],
				'job_offers'			=> $posted['job_offers'],
				'feat_job_offers'		=> $posted['feat_job_offers'],
				'access'				=> implode(',', $posted['access']),
				'job_cats'				=> implode(',', $job_cats),
				'pack_order'			=> ($posted['pack_order']>0?$posted['pack_order']:1),
			), array( 'id' => $edited_pack ), array( '%s','%s','%s','%s','%s','%s','%s','%s','%s','%s','%s' ) );