Pass PHP Variables from one plugin file to another WordPress
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I am working on a WordPress plugin and have run into a little road block. I am working on a part of the script that interacts with PayPal's IPN. I have an ipn.php file that is in the plugin directory, that file gathers the response from PayPal and verifies all the transaction details.
That part works fine, but the second part of this is I must insert the variables into the WordPress database to mark a successful purchase. 
Since $wpdb is not available in the ipn.php file, I must pass the data to the core of the plugin for processing.

I am open to other solutions on this and your help is much appreciated. Thanks!