Simple PHP Post-Redirect-Get code example

Question

I have found many sites that describes PRG, but no simple PHP code example.

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Here's what I implemented:

1. The form.php has an action: validate.php.
2. The validate.php is never seen by the user; if validates all $_GET and, if valid writes it to database and generates the HTML of a confirmation page / if not valid, it generates the HTML of an error page explaining what is wrong.
3. Whichever HTML is generated get stored in a $_SESSION variable and then validate.php calls header('Location: <as appropriate>);.
4. The submitted.php of invalid_input.php (in case the user reads the URL) consists only of echo $_SESSION['form_html'];.

That seems to me like protection against both page reload and back button problems.

Did I goof by trying to reinvent the wheel?

Answer 1

Simplest scenario:

if ($_POST) {
   // Execute code (such as database updates) here.

   // Redirect to this page.
   header( "Location: {$_SERVER['REQUEST_URI']}", true, 303 );
   exit();
}

Use REQUEST_URI. Do not use PHP_SELF as in most CMS systems and frameworks PHP_SELF would refer to /index.php.