Recently I created a database with a name test_test in phpMyAdmin and just after I created it, the list of database on the left hand side spoiled suddenly, Is this a bug or I should ignore _ in database name?
Preview
localhost screen


On selecting
test_testdatabase

PHPMyAdmin is grouping your databases if an underscore is used.
prefix_name. They still work like usual, they are just displayed differently in PHPMyAdmin.If you don’t like it you can disable it.