In the last part of this article, I am going to show you a simple example how to integrate the Facebook PHP SDK and Graph API into Opencart and auto publish products to Facebook Page. The example is a simplified version of my own script. You might want to modify this script on your shopping cart.

This script will randomly pick one of the published product from Opencart MySQL database and use the code in previous article for auto posting. By running the script under crob tab four times a day, for example, there are four product published everyday. 

This script is tested on Opencart 1.5.6.4.

Here is the sample code to do that:

After setting up Facebook App and getting a permanent Page Access Token, we now write a simple code to post a product to Facebook page. We need to download facebook PHP SDK v4 from github. You can get the file from here. Unzip the file and go to directory "Facebook". You can upload this directory to your server. 

Since v4.0.9, Facebook PHP SDK v4 come with autoloader, we don't have to use Composer (Dependency Manager for PHP). For the file downloaded just now, there is a file call "autoloader.php" before "src" directory. In my case, I moved this file into Facebook directory as well. 

Here is the code:

There are various types of access token for facebook app. The best article that explains them is How to handle access tokens with Facebook SDK v4.0 by Sammy Kaye. To post article / item / product from our own website to facebook fan page, we need to use Page Access Token.

The initial token can be obtained from Facebook Graph API tool. However, that is just a short-lived access token, which will expire in an hour or two after generation. We need to made a Graph API call to get a long-lived access token, which has two months expiry date. Lastly, get a permanent access token, which will never expire and can be used in our daily script.

We can test our script using short-lived access token, but then you have to regenerate another token after expiration. So we should directly get permanent access token before writing our script.

I have a ecommerce webstore using OpenCart with around 2000 products. I have created twitter, goolge+, pinterest and facebook page for this website. With Google moving towards semantic search, all these social signals are increasingly important. Everyday, I have to select one or two products and post on these social media websites. I don't like to do this manually and need to find ways to let a script doing the posting. For facebook page, I can use the APIs for daily auto posting. 

When I search for "Facebook PHP SDK for auto posting", there are lots of confusing results, mainly due to code written in different Facebook SDK versions. The documentation from Facebook developers website also quite difficult to understand. However, after reading articles from many websites, trial and error with example codes, finally I am able to do auto posting with Facebook PHP SDK v4 and Graph API v2.2.

Here's my expectations:

1) I want to auto post to Facebook Fan Page as admin.

2) No Login with Facebook required.

3) I want to post product title, product url, and product image, just like normal posting.

4) With 2000++ product listing and still increasing, I want able to auto post three to five items per day. It will take more that one year to post all products from my website. 

In part 1 of this article, I will describe how I set up facebook app. In the next article, I will describe the code used to auto post single item to facebook page.