PHP max_input_vars error

When exporting a large database of 2000 tables I am getting an error warning.  And when I proceed all I get is a source code for html page instead of sql file.

Please note the "export.php" part of error. 

Here is the scenario on both servers apache 2.2/centos6 and apache 2.4/centos7:

When I attempt to export a database with relatively few record but several hundred tables, I get the error you dont have permission to access /phpmyadmin/export.php.  However, if I select a single table and export, there is no error message. 

I might add, that on the centos7 server, I do get a warning ahead of time stating that :there is a form with more than 1000 fields" error.  My database might have several hundred tables, but I dont consider that very high.  I know that there is a php setting where I can bump that up.  My question is what should I bump it up and what is the down side to doing so?