Hi I am trying to compare the variable that a user would enter as the shipping state to a list of states for shipping this is my line of code where I am trying to say if the users shipping state is the same as one of the following:

Here is my code I am getting a parse error.. TY in advance all.

PHP Code:
if($_POST[ShippingState] == CaliforniaArizona, New MexicoColoradoUtahNevadaWyomingIdahoOregonWashingtonMontana