simple-location/simple-location.php

<?php

/*
Plugin Name: Simple Location
Plugin URI: http://www.danballard.com/
Description: Auto tags posts with city, country info 
Version: 0.1
Author: Dan Ballard
Author URI: http://www.danballard.com
Minimum WordPress Version Required: 3.8
Tested up to: 3.8
*/

if ( is_admin() ) {
  add_action( 'admin_menu', 'add_options_menu' );
  add_action( 'admin_init', 'reg_settings' );
  add_action( 'admin_menu', 'add_meta_to_edit' );
  add_action( 'edit_attachment', 'simple_location_post_save' );
  add_action( 'save_post', 'simple_location_post_save' );

}

function add_options_menu() {
  add_options_page('Simple Location Options', 'Simple Location', 'manage_options', 'simple-location', 'options_page');
}

function add_meta_to_edit() {
  add_meta_box('simple-location-meta', 'Simple Location', 'simple_location_meta', 'post', 'normal');
}

function simple_location_post_save($post_id) {
  if ($_POST['city'] == '' || $_POST['country'] == '') {
    $key = get_option('simple-location-api-key');
    if ($key != '') {
      include('ip2locationlite.class.php');
      $ipLite = new ip2location_lite;
      $ipLite->setKey($key);
      $locations = $ipLite->getCity($_SERVER['REMOTE_ADDR']);
      print_r($locations);
    }
  } 
  if ($_POST['city'] == '') {
    $_POST['city'] = $locations['cityName'];  
  }
  update_post_meta($post_id, '_simple_location_city', sanitize_text_field($_POST['city']));
  if ($_POST['country'] == '') {
    $_POST['country'] = $locations['countryName'];
  }
  update_post_meta($post_id, '_simple_location_country', sanitize_text_field($_POST['country']));
}

function simple_location_meta() {
  include( plugin_dir_path(__FILE__) . 'post-form.php');
}

function options_page() {
  include( plugin_dir_path(__FILE__) . 'options.php');
}

function reg_settings() {
  register_setting( 'simple-location-options', 'simple-location-api-key' );
}