In PHP, which is quicker; using include(\'somefile.php\')
or querying a MySQL database with a simple SELECT
query to get the same information?
It depends. If your file is stored locally in your server and the database is installed in another machine, then the faster is to include the file.
Buuuuut, because it depends on your system it could be not true. I suggest to you to make a PHP test script and run it 100 times from the command line, and repeat the test through HTTP (using cURL)
Example:
use_include.php
use_myphp.php