I was wondering if this is possible;

A user fills in the form, then after submitting (and clicking the continue button), shows the form again with filled in values of the previous.
Shortly: I would like to pre-fill fields with values of the previous form.

Is it is possible with $_POST["form"] or maybe only via the database?

In form properties >> tab form info >> submission you have the option for a thank you message. Enable this and you can get your fields bij typing in code like this: {Name:value} where name is the name of your desired field.

Hope this helps, its quite easy!

Yes, but those will give me the values on the "thank you" page...but I need a thank you page, then a button that leads me to the form again, with the values filled in before.

I found a bit of a workaround;
-Create your RSForm (1);
-Disable thank you message and button and no URL here.
-Turn on Silent Post
-Create a blank thankyou.php page and lead silent post to this page.
-Make a form (2)in HTML/PHP with fields you want to keep for the next form
-Make a submit button like; "Fill in another form"
-In <form action=""> ise URL of your RSform (1)
-In RSForm, for fields you want pre-filled;
//<code>
return $_POST["FIELDNAME"];
//</code>

Its a bit too much work.
Im gonna try it with the thank you page.

OK. this is a bit easier;

In scripts->thankyoumessage;

$thankYouMessage= '
<form id="[ANYTHING]" action="[URL_OF_THE_FORM]" method="post">
<input name="Name" value="'.$_POST["form"]["Name"].'"/>
<input type="submit" name="fill in another form">
</form>';

THen use the same //code as above