How to refactor this WordPress query?

I am using query_vars in my function.php to get some data in my URL after a form is submitted. This is all working fine, however I feel like the code can be improved a lot, but I’m not sure how to refactor this.

function add_query_vars(
 $membership_vars
) {
 $membership_vars[] = "firstName";
 $membership_vars[] = "membership";
 $membership_vars[] = "subscription";
 $membership_vars[] = "total";
 return $membership_vars;
}

add_filter('query_vars', 'add_query_vars');

And then in a custom page template (PHP) I am displaying this on the page like this:

$firstName = urldecode($wp_query->query_vars['firstName']);
$membership = urldecode($wp_query->query_vars['membership']);
$subscription = urldecode($wp_query->query_vars['subscription']);
$total = urldecode($wp_query->query_vars['total']);

<section>
 <p>Congratulations <?php echo $firstName ?>!</p>
 <p>You have chosen: <?php echo $membership ?> 
 <p>You have subscribed to: <?php echo $subscription ?> 
 <p>Your total paid is: <?php echo $total ?> 
</section>

As you can see the code isn’t DRY, however as mentioned I’m not sure how to refactor this in PHP.

Answer

Maybe you can try something like this:

function add_query_vars( $membership_vars ) {
 $params = array( 'firstName', 'membership', 'subscription', 'total' );
 
 foreach ( $params as $param ) {
   $membership_vars[] = $param;
 }

 return $membership_vars;
}

add_filter('query_vars', 'add_query_vars');

and then in the template:

$params = array( 'firstName', 'membership', 'subscription', 'total' );
$values = array();

foreach ( $params as $param ) {
  $values[$param] = urldecode( get_query_var($param, '') );
}

<section>
 <p>Congratulations <?php echo esc_html( $values['firstName'] ); ?>!</p>
 <p>You have chosen: <?php echo esc_html( $values['membership'] );?> 
 <p>You have subscribed to: <?php echo esc_html( $values['subscription'] ); ?> 
 <p>Your total paid is: <?php echo esc_html( $values['total'] ); ?> 
</section>