Using PHP Within WordPress- 5.2 vs 5.5

I have custom forms that I build myself inside WordPress and I use PHP to process them. I write all the code and scripts on the page files themselves NOT within the WordPress admin interface. For instance I create a “page-myform.php” page and write the form on that and then it goes to a “page-processmyform.php” page where I write the PHP to process the form. I’ve been doing this for years, never had any problems. One thing I’ve always found is that I didn’t need to establish a database connection before inserting or retrieving info from the MySQL database, I assumed because WordPress had already made the connection.

Recently my host updated my account from 5.2 to 5.5.18. Suddenly, none of my forms worked anymore. After a lot of trial and error it seems that the only problem is that I now need to actually make a database connection in my code, unlike before. Then things seem to work again.

Can anyone confirm that switching from PHP 5.2 to 5.5.18 would require that I now make a database connection each time I want to send a form or pull results from the database? Thanks for any insight into this issue.