Here are a couple of comments, by no means trying to be complete:

I think you made a good start with your Employee class. If this is going to be grown beyond this one table, then you may want to inherit from a "Table" class, which at least has the constructor and probably the $db in it

Recommend you combine fetchBy and fetchEmployee into 1 function for the following reasons:

• $employee->fetchEmployee unnecessary duplication of what you are fetching
• unnecessary employee attribute can be eliminated

Why is $type defaulted to username. It seems not obvious to me. Some frameworks use id as a default, I think that is a better option

The switch statement can be simplified, see how you repeat the code for each parameter type? You only need one block of code for PDO::PARAM_STR, PARAM_INT etc

Recommend you always use fetchAll and create another indirection through a new function called fetchOneBy()

Using * in queries has no direct downside at this level of complexity, however once you start using joins, it will get you into trouble. However you'll quickly find that listing the columns will be tedious. The natural tendency is to then build a data dictionary, for example by using private variables (see Joomla) or having a getFields() function in each class. Don;t go to far down this rabbit hole, as this problem has been solved many times over: https://packagist.org/packages/doctrine/orm

Hope this helps.

Here are a couple of comments, by no means trying to be complete:

I think you made a good start with your Employee class. If this is going to be grown beyond this one table, then you may want to inherit from a Table class, which at least has the constructor and probably the $db in it

Recommend you combine fetchBy and fetchEmployee into 1 function for the following reasons:

• $employee->fetchEmployee unnecessary duplication of what you are fetching
• unnecessary employee attribute can be eliminated

Why is $type defaulted to username. It seems not obvious to me. Some frameworks use id as a default, I think that is a better option

The switch statement can be simplified, see how you repeat the code for each parameter type? You only need one block of code for PDO::PARAM_STR, PARAM_INT etc

Recommend you always use fetchAll() and create another indirection through a new function called fetchOneBy().

Using * in queries has no direct downside at this level of complexity, however once you start using joins, it will get you into trouble. However you'll quickly find that listing the columns will be tedious. The natural tendency is to then build a data dictionary, for example by using private variables (see Joomla) or having a getFields() function in each class. Don't go to far down this rabbit hole, as this problem has been solved many times over: https://packagist.org/packages/doctrine/orm