PHP "SHOW TABLES" MySQLi query not working

You cannot concatenate like that in mySQL, or any form of SQL I can think of.

SHOW TABLES LIKE ?_?_?

Should be:

SHOW TABLES LIKE CONCAT(?, '_', ?, '_', ?) --this gives an error, see below

And I fully agree with @your-common-sense's commentary that this is a terrible way to design a database and you will come to regret it in more ways than just this one messed up query.

edit:

MySQL does not seem to allow functions in a SHOW TABLES statement, so either you'll have to concatenate the table name to a single string in PHP, or you can use a query like:

SELECT 
  TABLE_NAME
FROM    
  INFORMATION_SCHEMA.TABLES    
WHERE    
  table_schema = 'mydb' AND    

  table_name LIKE CONCAT(?, '_', ?, '_', ?);