PHP / WORDPRESS - Mailchimp Sub

main.js

jQuery(document).ready(function($) {  
  
  function list_sub(form, btn){

    input = {
      action   : 'actionSubscribe',
      group_id : $('.form-subscribe input[name=form-subscribe-type]:checked').val(),
      fname    : form.find('.inputFname').val(),
      lname    : form.find('.inputLname').val(),
      email    : form.find('.inputEmail').val(),
    }

    btn.addClass('active');
    btn.text('One Moment...');

    $.post("/wp-admin/admin-ajax.php", input, function(output){
      if( output["success"] == 1){
        form.hide();
        btn.hide();
        $('.modal-subscribe .btn-secondary').show();
        $('.modal-subscribe .form-success').show();
      } else {
        form.find('.form-error').html( output["message"] ).show();
      }
    }, 'JSON').fail(function(xhr, desc, err) {
      console.log( xhr + " " + desc);
      alert( err );
    });

  }
  
});

main.php

<?php 

function mailchimp_subscribe(){

  // Ajax
  $fname    = $_POST['fname'];
  $lname    = $_POST['lname'];
  $email    = $_POST['email'];
  $user_id  = $_POST['user_id'];
  $group_id = $_POST['group_id'];

  //Vars
  $list_id = '16e0b3a56a';
  $out = array('success' => 0 );

  // API
  $data_center = 'us3';
  $api = 'c2e80b596fc40dab093fe96f400f85dd' . '-' . $data_center;
  $auth = base64_encode( 'user:' . $api );

  // Data
  $data = array(
    'method'  => 'PUT',
    'headers' => array(
      'Authorization' => 'Basic ' . $auth
    ),
    'body' => json_encode(array(
      'email_address' => $email,
      'status'        => 'subscribed',
      'merge_fields'  => array(
        'FNAME' => $fname,
        'LNAME' => $lname
      ),
      'interests' => array(
        $group_id => true
      )
    ))
  );

  $response = wp_remote_post( "https://$data_center.api.mailchimp.com/3.0/lists/$list_id/members/" . md5(strtolower($email)), $data );
  $body = json_decode( $response['body'] );

  if ( $response['response']['code'] == 200 ) {
    $out['success'] = 1;
  	$out['response'] = 'The user has been successfully ' . $status . '.';
  } else {
  	$out['response'] = '<b>' . $response['response']['code'] . $body->title . ':</b> ' . $body->detail;
  }

  //Return
  echo json_encode($out);
  wp_die();

}

add_action( 'wp_ajax_nopriv_actionSubscribe', 'mailchimp_subscribe' );
add_action( 'wp_ajax_actionSubscribe', 'mailchimp_subscribe' );

?>