Best way to integrate an existing PHP application into WordPress
A client of ours has a web application written in PHP. They have commissioned us to develop the front end for the website, but they want us to integrate the current PHP web application (a package tracking system) into the WordPress site (our choice). What’s the best practice to do this? Making the existing application into a plugin? Is that an approach?
Right now, the existing web application requires login and then establishes a session with the user. Can this web application co-exist within WordPress or do we just need to <IFRAME> it in or just link to it as a separate application?
Are there any best practices for this sort of thing?