I need some help. I want to know using php sql to use OR in a query.

Let me explain in detail:

I have a html form which asks the user for country,state,c ity,zip_code

I will use these values to query the database for specific data for those specific inputs.

I want the city and zip_code to be logicly use as OR. Meaning that the user only needs to select a city or type the exact zip_code....