How do I pass form data to the next form page after sending to a php mailto page?

I have a few forms on my website which I need site visitors to submit in sequence.

‘form1’ sends the user data to the (php mailto) form mailer.

The header(location) of the form mailer then directs the site visitor to a page with ‘form2’.

I need a php solution to pre-populate form2 with the previously submitted data from form1.

I would like a slicker alternative to passing the data through the URL.

Form 1:

<form id="form1" action="formMailer.php" method="post">
   Name:&nbsp;<input type="text" id="userName" name="userName" value="">
   Email:&nbsp;<input type="email" id="userEmail" name="userEmail" value="">
<input type="submit" id="submitButton" name="submitButton" value="Submit">

PHP Form Mailer:

<?php 

    $name = $_POST['userName']; 
    $email = $_POST['userEmail']; 

    $message =

       "rnYour Name: "  .$name .
       "rnYour Email: "  .$email;

    $subject ="Subject of email";

    $mailto = "[email protected]";

    $separator = md5(uniqid(time()));

    $eol = "rn";

$headers = "From: ".$name." <".$email.">" . $eol;
$headers .= "MIME-Version: 1.0" . $eol;
$headers .= "Content-Type: multipart/mixed;". $eol. " boundary="" . $separator . """ .  $eol;
$headers .= "This is a MIME encoded message." . $eol . $eol;

$body = "--" . $separator . $eol;
$body .= "Content-Type: text/plain; charset="iso-8859-1"" . $eol;
$body .= "Content-Transfer-Encoding: 8bit" . $eol . $eol;
$body .= $message . $eol;

   mail($mailto, $subject, $body, $headers);

   header('location: /formFolder/form2.php');

?>

Form 2:

<form id="form2" action="nextAction" method="post">
   Name:&nbsp;<input type="text" id="userName" name="userName" value="">
   Email:&nbsp;<input type="email" id="userEmail" name="userEmail" value="">
   Other Data:&nbsp;<input type="text" id="other_userData" name="other_userData" value="">
<input type="submit" id="submitButton" name="submitButton" value="Submit">

I tried some php ‘get’ and ‘echo’ script, but it seems the data gets lost somewhere between the mailto and the second form.