Question

What is proper way to process forms in http?

on /somepage:

<form method="POST" action="/someaction.html">
    <input type="text" name="name">
    <input type="submit">
</form>

Let’s assume, that user didn’t filled in “name”. So I should produce some error. How should I do it:

First method

1. POST /someaction and 302 Redirect to /posterror?error=1
2. GET /posterror?error=1 and 200 Ok with content about errors and form

Second

1. POST /someaction and 200 Ok with content about errors and form

Third

1. POST /someaction, remember in session form errors and 302 Redirect to /posterror
2. GET /posterror and 200 Ok with content about errors and form

Which one is proper way? Maybe some fourth one?

Answer 1

The correct approach is called post/redirect/get and is described by wikipedia as:

Post/Redirect/Get (PRG) is a common design pattern for web developers
to help avoid certain duplicate form submissions and allow user agents
to behave more intuitively with bookmarks and the refresh button.