Dynamic input characters box

[tempph]

Hi all, (big newb here)

I’m making a very simple page, where the user enters text or numbers in an input box (maybe with some html “form action” tools), clicks a button and it will display something, e.g. the double value of the number entered.

The trick is, I need two things :

1. the page won’t reload, nor get a new page giving input box arguments. I’d like it to be instant. I don’t even have any idea what language should I be looking for for this. I suppose php could do.
2. I’d like the original characters to remain in the input box

Any help where i should be looking for ?

Ty !

[xerxes]

I would use JavaScript, something like this:

[php]

[/php]