Or, you can escape the apostrophe with the backslash ( \ ) such as:
define('TEXT_INFORMATION','You can add items to your shopping cart by either using our search engine to find the item(s) that you wish to purchase or by browsing through our categories and/or our website. Once you find an item(s) you\'d like to buy, simply hit the "BUY NOW" button closest to the item(s) you are interested in to add the selected item(s) to your shopping cart. At this point, you can change the quantity of items you\'d like to order, delete an item, empty the shopping cart, continue shopping, or proceed to check out.');