Please note: this script no longer work
A few years back, I found a PHP wrapper of Instagram API and it is simple enough for me to craft a simple web application. So I create an app call Instacheck, an very common application for instagram user to check who not following you back. The application also allow the user to easily unfollow the user that did not follow you back with a single click.
Here the link to my app called Instacheck (No longer active)
The code is also open source and can be pull at Github Please note, that the code is ugly as hell but it’s perfectly functional. You are very welcome to refractor the code into more organize way.
To install the application, just edit the config.php file with your Instagram client_id and client_secret Developer API and also don’t forget to change the redirect_uri to your domain. Then you’re good to go.
The application works by pulling a list of your follower and following and store them in separate array and use the PHP array_diff function to get the list of your unfollowers. This may or may not be the most optimize way, in exception of using local cache blah blah blah, anyways if you know a better way to get the list of unfollowers please let me know in the comment.