When do you use POST and when do you use GET?

Question

From what I can gather, there are three categories:

1. Never use GET and use POST
2. Never use POST and use GET
3. It doesn't matter which one you use.

Am I correct in assuming those three cases? If so, what are some examples from each case?

Answer 1

1.3 Quick Checklist for Choosing HTTP GET or POST

Use GET if:

    The interaction is more like a question (i.e., it is a safe operation such as a query, read operation, or lookup).

Use POST if:

    The interaction is more like an order, or
    The interaction changes the state of the resource in a way that the user would perceive (e.g., a subscription to a service), or
    The user be held accountable for the results of the interaction.

Source.

Answer 2

Read the article about HTTP in the Wikipedia. It will explain what the protocol is and what it does:

GET

Requests a representation of the specified resource. Note that GET should not be used for operations that cause side-effects, such as using it for taking actions in web applications. One reason for this is that GET may be used arbitrarily by robots or crawlers, which should not need to consider the side effects that a request should cause.

and

POST Submits data to be processed (e.g., from an HTML form) to the identified resource. The data is included in the body of the request. This may result in the creation of a new resource or the updates of existing resources or both.

The W3C has a document named URIs, Addressability, and the use of HTTP GET and POST that explains when to use what. Citing

1.3 Quick Checklist for Choosing HTTP GET or POST

• Use GET if:
  • The interaction is more like a question (i.e., it is a safe operation such as a query, read operation, or lookup).

and

• Use POST if:
  • The interaction is more like an order, or
  • The interaction changes the state of the resource in a way that the user would perceive (e.g., a subscription to a service), or o The user be held accountable for the results of the interaction.

However, before the final decision to use HTTP GET or POST, please also consider considerations for sensitive data and practical considerations.

A practial example would be whenever you submit an HTML form. You specify either post or get for the form action. PHP will populate $_GET and $_POST accordingly.

Answer 3

From w3schools.com:

What is HTTP?

The Hypertext Transfer Protocol (HTTP) is designed to enable communications between clients and servers.

HTTP works as a request-response protocol between a client and server.

A web browser may be the client, and an application on a computer that hosts a web site may be the server.

Example: A client (browser) submits an HTTP request to the server; then the server returns a response to the client. The response contains status information about the request and may also contain the requested content.

Two HTTP Request Methods: GET and POST

Two commonly used methods for a request-response between a client and server are: GET and POST.

GET – Requests data from a specified resource POST – Submits data to be processed to a specified resource

Here we distinguish the major differences:

Answer 4

i dont see a problem using get though, i use it for simple things where it makes sense to keep things on the query string.

Using it to update state - like a GET of delete.php?id=5 to delete a page - is very risky. People found that out when Google's web accelerator started prefetching URLs on pages - it hit all the 'delete' links and wiped out peoples' data. Same thing can happen with search engine spiders.

Answer 5

The original intent was that GET was used for getting data back and POST was to be anything. The rule of thumb that I use is that if I'm sending anything back to the server, I use POST. If I'm just calling an URL to get back data, I use GET.

Answer 6

Use GET when you want the URL to reflect the state of the page. This is useful for viewing dynamically generated pages, such as those seen here. A POST should be used in a form to submit data, like when I click the "Post Your Answer" button. It also produces a cleaner URL since it doesn't generate a parameter string after the path.