WordPress Recaptcha Problem (please Help)

functions.php

<?php

// Link or Import the database.php file (SQL structure)
require get_template_directory() . '/inc/database.php';
// Handles submission to database
require get_template_directory() . '/inc/reservations.php';
// Create option pages for the theme
require get_template_directory() . '/inc/options.php';


function lapizzeria_setup() {
add_theme_support('post-thumbnails');

add_image_size('boxes', 437, 291, true );
add_image_size('specialties', 768, 515, true);

add_image_size('specialty-portrait', 435, 530, true);

update_option('thumbnail_size_w', 253);
update_option('thumbnail_size_h', 164);

add_theme_support('title-tag');


}
add_action('after_setup_theme', 'lapizzeria_setup');


function lapizzeria_custom_logo() {
  $logo = array(
    'height' => 200,
    'width' => 250
  );
  add_theme_support('custom-logo', $logo);
}
add_action('after_setup_theme', 'lapizzeria_custom_logo');


function lapizzeria_styles() {
  // adding style
  wp_register_style('googlefont', 'https://fonts.googleapis.com/css?family=Open+Sans:400,700|Raleway:400,700,90', array(), '1.0.0');
  wp_register_style('normalize', get_template_directory_uri() . '/css/normalize.css', array(), '8.0.0' );
  wp_register_style('fluidboxcss', get_template_directory_uri() . '/css/fluidbox.min.css', array(), '1.0.0' );
  wp_register_style('fontawesome', get_template_directory_uri() . '/css/font-awesome.css', array(), '4.7.0' );
  wp_register_style('datetime-local', get_template_directory_uri() . '/css/datetime-local-polyfill.css', array(), '1.0.0' );
  wp_register_style('style', get_template_directory_uri() . '/style.css', array('normalize'), '1.0' );

  // Enqueue the STYLE
  wp_enqueue_style('normalize');
  wp_enqueue_style('fluidboxcss');
  wp_enqueue_style('fontawesome');
  wp_enqueue_style('datetime-local');
  wp_enqueue_style('googlefont');
  wp_enqueue_style('style');

  $apikey = esc_html(get_option('lapizzeria_gmap_apikey'));
  wp_register_script('fluidboxjs', get_template_directory_uri() . '/js/jquery.fluidbox.min.js', array('jquery'), '1.0.0', 'true');
  wp_register_script('googlemaps', 'https://maps.googleapis.com/maps/api/js?key=' . $apikey . '&callback=initMap', array(), '', true);
  wp_register_script('datetime-local-polyfill', get_template_directory_uri() . '/js/datetime-local-polyfill.min.js', array('jquery', 'jquery-ui-core', 'datetime-ui-datepicker', 'modernizr'), '1.0.0', 'true');
  wp_register_script('script', get_template_directory_uri() . '/js/scripts.js', array('jquery'), '1.0.0', 'true');
  wp_register_script('modernizr', 'https://cdnjs.cloudflare.com/ajax/libs/modernizr/2.8.3/modernizr.min.js', array('jquery'), '2.8.3', true);
  wp_register_script('recaptcha', 'https://www.google.com/recaptcha/api.js');

  // Add javaScript files
  wp_enqueue_script('jquery');
  wp_enqueue_script('jquery-ui-core');
  wp_enqueue_script('jquery-ui-datepicker');
  wp_enqueue_script('datetime-local-polyfill');
  wp_enqueue_script('modernizr');
  wp_enqueue_script('fluidboxjs');
  wp_enqueue_script('googlemaps');
  wp_enqueue_script('recaptcha');
  wp_enqueue_script('script');

  wp_localize_script(
    'script',
    'options',
    array(
      'latitude' => esc_html(get_option('lapizzeria_gmap_latitude') ),
      'longitude' => esc_html(get_option('lapizzeria_gmap_longitude') ),
      'zoom'      => esc_html( get_option('lapizzeria_gmap_zoom') )
    )
  );


}
add_action('wp_enqueue_scripts', 'lapizzeria_styles');

function lapizzeria_admin_scripts() {
  // Sweet Alert 2
  wp_enqueue_style('sweetalert', get_template_directory_uri() . '/css/sweetalert2.min.css');
  wp_enqueue_script('sweetalertjs', get_template_directory_uri() . '/js/sweetalert2.min.js', array('jquery'), 1.0, true);

// Admin script
  wp_enqueue_script('adminjs', get_template_directory_uri() . '/js/admin_ajax.js', array('jquery'), 1.0, true);



  wp_localize_script(
    'adminjs',
    'admin_ajax',
    array('ajaxurl' =>  admin_url('admin-ajax.php') )
  );

}
add_action('admin_enqueue_scripts', 'lapizzeria_admin_scripts');

// Add menus
function lapizzeria_menus() {
  register_nav_menus(array(
    'header-menu' => __('Header Menu', 'lapizzeria'),
    'social-menu' => __('Social Menu', 'lapizzeria')
  ));
}

add_action('init', 'lapizzeria_menus');



function lapizzeria_specialties() {
	$labels = array(
		'name'               => _x( 'Pizzas', 'lapizzeria' ),
		'singular_name'      => _x( 'Pizza', 'post type singular name', 'lapizzeria' ),
		'menu_name'          => _x( 'Pizzas', 'admin menu', 'lapizzeria' ),
		'name_admin_bar'     => _x( 'Pizzas', 'add new on admin bar', 'lapizzeria' ),
		'add_new'            => _x( 'Add New', 'book', 'lapizzeria' ),
		'add_new_item'       => __( 'Add New Pizza', 'lapizzeria' ),
		'new_item'           => __( 'New Pizzas', 'lapizzeria' ),
		'edit_item'          => __( 'Edit Pizzas', 'lapizzeria' ),
		'view_item'          => __( 'View Pizzas', 'lapizzeria' ),
		'all_items'          => __( 'All Pizzas', 'lapizzeria' ),
		'search_items'       => __( 'Search Pizzas', 'lapizzeria' ),
		'parent_item_colon'  => __( 'Parent Pizzas:', 'lapizzeria' ),
		'not_found'          => __( 'No Pizzas found.', 'lapizzeria' ),
		'not_found_in_trash' => __( 'No Pizzas found in Trash.', 'lapizzeria' )
	);

	$args = array(
		'labels'             => $labels,
    'description'        => __( 'Description.', 'lapizzeria' ),
		'public'             => true,
		'publicly_queryable' => true,
		'show_ui'            => true,
		'show_in_menu'       => true,
		'query_var'          => true,
		'rewrite'            => array( 'slug' => 'specialties' ),
		'capability_type'    => 'post',
		'has_archive'        => true,
		'hierarchical'       => false,
		'menu_position'      => 6,
		'supports'           => array( 'title', 'editor', 'thumbnail' ),
    'taxonomies'          => array( 'category' ),
	);

	register_post_type( 'specialties', $args );
}

add_action( 'init', 'lapizzeria_specialties' );


/** Widgets **/
function lapizzeria_widgets() {
  register_sidebar( array(
    'name' => 'Blog Sidebar',
    'id'   => 'blog_sidebar',
    'before_widget' => '<div class="widget">',
    'after_widget' =>  '</div>',
    'before_title' =>  '<h3>',
    'after_title' =>   '</h3>'
  ) );
}

add_action('widgets_init', 'lapizzeria_widgets');

function add_async_defer($tag, $handle) {
  if('googlemaps' !== $handle) {
    return $tag;
 }
  return str_replace(' src', 'async="async" defer="defer" src', $tag);
}

add_filter('script_loader_tag', 'add_async_defer', 10, 2);



?>

reservation-form.php

<div class="reservation-info">
  <form class="reservation-form" method="post">
    <h2>Make a Reservation</h2>
    <div class="field">
      <input type="text" name="name" placeholder="Name" required>
    </div>
    <div class="field">
      <input type="datetime-local" name="date" placeholder="Date" step="300" required>
    </div>
    <div class="field">
      <input type="email" name="email" placeholder="E-Mail" required>
    </div>
    <div class="field">
      <input type="tel" name="phone" placeholder="Phone Number" required>
    </div>
    <div class="field">
      <textarea name="message" placeholder="Message" required></textarea>
    </div>

    <div class="g-recaptcha" data-sitekey="6Lc3Am0UAAAAAMlV93owh3VwsqNtZ0CoE1duhfCd"></div>

    <input type="submit" name="reservation" class="button" value="Send">

    <input type="hidden" name="hidden" value="1">
  </form>
</div>

reservations.php

<?php

function lapizzeria_delete_reservation() {


    if($_POST['type'] == 'delete'):
        global $wpdb;
        $table = $wpdb->prefix . 'reservations';
        $id_reservation = $_POST['id'];

        $result = $wpdb->delete($table, array('id' => $id_reservation), array('%d') );

        if($result == 1) {
            $response = array(
                'response' => 'success',
                'id' => $id_reservation
            );
        } else {
            $response = array(
                'response' => 'error'
            );
        }

    endif;

    die(json_encode($response));
}
add_action('wp_ajax_lapizzeria_delete_reservation', 'lapizzeria_delete_reservation');

function lapizzeria_save_reservation() {

    if(isset($_POST['reservation']) && $_POST['hidden'] == "1") {
              // read the value from recaptcha response
              $captcha = $_POST['g-recaptcha-response'];

              // Send the values to the server
              $fields = array(
            'secret'   => '6Lfk8GwUAAAAADATVwVH16LJv4SGkkrYFos02_eo',
            'response' => $captcha,
                  'remoteip' => $_SERVER['REMOTE_ADDR']
              );

              // Start the request to the server
              $ch = curl_init('https://www.google.com/recaptcha/api/siteverify');

                  // configure the request
                  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                  curl_setopt($ch, CURLOPT_TIMEOUT, 15);

                  // Send the encode values in the URL
                  curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($fields));

                  // Read the return value
                  $response = json_decode(curl_exec($ch));
                  if($response->success) {
                              global $wpdb;
                              $name = sanitize_text_field( $_POST['name'] ) ;
                              $date = sanitize_text_field( $_POST['date'] ) ;
                              $email = sanitize_email( $_POST['email'] );
                              $phone = sanitize_text_field( $_POST['phone'] ) ;
                              $message = sanitize_text_field( $_POST['message'] ) ;

                              $table = $wpdb->prefix . 'reservations';

                              $data = array(
                                'name' => $name,
                                'date' => $date,
                                'email' => $email,
                                'phone' => $phone,
                                'message' => $message
                              );

                              $format = array(
                                '%s',
                                '%s',
                                '%s',
                                '%s',
                                '%s'
                              );
                              $wpdb->insert($table, $data, $format );

                              $url = get_page_by_title('Thanks for your reservation!');
                              wp_redirect( get_permalink($url) );
                              exit();
                  }


        }
    }

add_action('init', 'lapizzeria_save_reservation');

?>

https://core.trac.wordpress.org/ticket/44832