Flash messages are messages that are displayed to the client - usually after some action has been performed.
If the client has logged in, then it is normal to display a message like Welcome. You are now logged in.
In the following example we make two routes, / and /click.
The / route just shows a link, that says Click me. When
clicking this link we navigate to /click which sets a flash message
in the $_SESSION['flash'] variable.
Then we are redirected back to /, where the flash messages are
displayed and cleared.
We execute this controller in our index.php file:
Run the example:
php -S localhost:8000 -t examples/flash
You may then visit http://localhost:8000