I'm tyring to figure out a way to compare the information in 2 different tables from 2 different databases. If they are in the same database it's easy enough but I haven't found a way to do it from 2 different databases.

Hello Henryu,

Although in the PDO DB connection object constructor you define the default schema there is nothing stopping you from selecting from other one or using JOIN with two different schemas in the same server as long as:
A: The user has sufficient privileges in both schemas
B: You add the schema prefix (with dot) before the table name (e.g. example_db.categories)