I'm confused how to proceed with creating a user defined function (PHP) : I'm taking a highschool CS class but the one homework question is really confusing me. So essentially, I'm supposed to create a function that uses 2 arguments. Both of the arguments are strings. One of the arguments is this text (Placeholder text here.) and the other argument is a letter, either A or B. If it's A, I need to change the case using the built in php function of the text to upper case. If it's B, I need to change the case using the built in php function of the text to lower case.

Okay, so I know I have to use an elseif statement, but I'm just not sure how I should proceed. If anyone could give me some starters that would be much appreciated. 

Thank you for reading!