How do you show values of php variables instead of the name of php variables when using the get method through a php redirect. prepop

Question

I am having trouble showing the values prepoped on the page i clicked on after the redirect. This is my first page

<form action="go.php" method="get">
<input type="text" name="email" size="30"/>
<input type="submit" value="Submit"/>
</form>

and this is my redirect page

<?php
$email = $_GET['email'];
header('Location: https://testlink.com/test?&email=$email', true, 301);
exit;
?>

And on the page after the php redirect it is showing me the variable name $email in the prepopulated email field of the email form instead of the value of $email 'which is where the user types in their email on the first page'. How do you show the value of the variable $email in the prepopulated email field instead of the variable name?