Functions are groups of operations and tasks that allow for the performing of complex tasks and manipulations.

PHP provides built-in functions with existing arguements to pass parameters into and the ability to define user-defined functions.

The first example demonstrates the "substr" built-in function, which returns values from a string based on the parameters defined in the function.

The second example uses a user-defined function titled "add_tax". It accepts a single arguement of "$price".
That value is multiplied by one of the Milwaukee sales tax rates, and then that product is assigned to the variable "$total"

The total price is 10.78