1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '18'') limit 1' at line 5
in:
[select p2c.categories_id, p.master_categories_id from products p, products_to_categories p2c where p.products_id = '275' and p.products_id = p2c.products_id and (p.master_categories_id = '18'' or p2c.categories_id='18'') limit 1]