I have configured a Wordpress site for a client for which the content has been migrated from a static HTML site from 2004.
The old site has a link which takes the user to a PHP form (also developed in 2004) which is hosted on a separate domain. This PHP page queries a MySQL database also hosted on the separate domain.
I have been asked if I can make this PHP form appear as part of the new Wordpress site rather than as a link to an external site.
Currently the most straight forward option I can think of is to modify the styling used by the PHP form and then embed it using an iFrame. Alternatively I could try and build a form in Wordpress that will query the MySQL database on a separate domain, but this seems like a lot of work and may have security implications.
Given I am relatively inexperienced with Wordpress what other options are there for doing this?