There are situations where you need to pass multiple values for the same parameter to the server, here are some patterns.

• Multiple checkboxes to pick the values for the same purpose.
  • Select columns to show in the table
  • Select post categories
• User can add as much values as he/she likes.
  • Add new tag
  • Add language
• User can remove multiple items from a list.
  • Remove items from shopping cart

This can be handled by passing many values in one parameter with a common delimiter, or by passing multiple values as the same parameter. Here are examples with the GET method, for the POST it works the same.