WordPress Plugin Development

1. Istanbul WordPress Meetup
February 16, 2019

2. Plugin Development
Mostafa Soufi
Founder and CTO
Customer Support
Navid Kashani
Co-Founder and Project Manager

3. Plugin Development
Mostafa Soufi

4. Why We Make Plugins?
Don’t touch WordPress core

5. What is a Plugin?
WordPress plugins are made up of PHP code and other
assets such as images, CSS, and JavaScript.

6. Getting Started
$ cd wp-content/plugins
$ mkdir plugin-name
$ touch plugin-name/plugin-name.php
wp-content/plugins/plugin-name/plugin-name.php

7. Readme file
=== Plugin Name ===
Contributors: (this should be a list of wordpress.org userid's)
Donate link: http://example.com/
Tags: comments, spam
Requires at least: 3.0.1
Tested up to: 3.4
Requires PHP: 5.2.4
Stable tag: 4.3
License: GPLv2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Here is a short description of the plugin.

8. Folder Structure
plugin-name
├── includes
│ ├── admin
│ │ ├── assets
│ │ │ └── Admin assets
│ │ └── Admin files
│ └── Core files
├── public
│ ├── assets
│ │ └── Front assets
│ └── Front files
└── languages

9. Suggestions

10. Enable Debugging Mode
<?php
// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );

11. Not to echo <script> and <style> tags directly
<?php
function add_plugin_assets() {
wp_enqueue_style( plugin-css, 'style.css', false );
wp_enqueue_script( 'plugin-js', 'filename.js', false );
}
add_action( 'wp_enqueue_scripts', 'add_plugin_assets' );

12. Avoid Naming Collisions
Fatal error: Cannot redeclare
subscribe() previously declared
<?php
// wp-content/plugin-1/plugin-1.php
function subscribe() {
return 'foo';
}
// wp-content/plugin-2/plugin-2.php
function subscribe() {
return 'bar';
}

13. Avoid Naming Collisions
// wp-content/plugin-1/plugin-1.php
namespace Plugin1;
function subscribe() {
return 'foo';
}
// wp-content/plugin-2/plugin-2.php
namespace Plugin2;
function subscribe() {
return 'bar';
}

14. Prefix Everything
<?php
// Your function
function pn_get_posts()
{
}
<?php
// Your constant
define('PN_VERSION', '1.0);

15. Check for Existing Implementations
PHP provides a number of functions to verify
the existence of variables, functions, classes,
and constants. All of these will return true if the
entity exists.

16. For variables: isset()
$data = $wpdb->get_row("SELECT * FROM mytable");
if (isset($data->name)) {
}
$option = get_option('your_option');
if (isset($option['status'])) {
}
Array Object

17. For functions: function_exists()
<?php
if (!function_exists('is_admin')) {
require_once(ABSPATH . 'wp-admin/includes/load.php');
}
if (!function_exists('post_exists')) {
require_once(ABSPATH . 'wp-admin/includes/post.php');
}

18. For classes: class_exists()
<?php
if (class_exists('WooCommerce')) {
// code that requires WooCommerce
} else {
// you don't appear to have WooCommerce activated
}

19. For constants: defined()
<?php
if (!defined('CONSTANT')) {
define('CONSTANT', 'constant_value');
}

20. Conditional Loading
<?php
if ( is_admin() ) {
// We are in admin mode
require_once( dirname( __FILE__ ) . '/includes/admin/admin.php' );
require_once( dirname( __FILE__ ) . '/includes/admin/setting.php' );
}

21. Hooks
Action / Filter

22. Actions
Actions provide a way for running a function at
a specific point in the execution of WordPress
Core, plugins, and themes.

23. Create a new action
$result = $wpdb->delete( $table, array( 'id' => $id ) );
if ( $result ) {
do_action( 'pluginname_remove', $id );
return true;
}
// Send an email to admin when an item removed.
add_action( 'pluginname_remove', function ( $item_id ) {
wp_mail( 'admin@example.com', "Item {$item_id} removed", 'Email content' );
} );

24. Filters
Filters provide a way for functions to modify
data of other functions.

25. Create a new filter
function get_name() {
$value = ‘Sara’;
return apply_filters(‘filter_name’, $value);
}
// Run Filter
add_filter('filter_name', function( $value ){
return 'Hello ' . $value;
});
// Return Sara
echo get_name();
// Return Hello Sara
echo get_name();

26. Plugin Features

27. Shortcode
[audio], [caption], [embed], [gallery], [playlist], [video]
Shortcode is the best way to show the PHP
functions in the WordPress Editor and Widgets

28. Create a new Shortcode
function pn_show_users() {
echo date('Y-m-d');
}
// [pluginname-date]
function shortcode_function( $atts ) {
return pn_show_users();
}
add_shortcode( 'pluginname-date', 'shortcode_function' );

29. Internationalization (i18n)
Internationalization is the process of developing
your plugin so it can easily be translated into
other languages.

30. Enable i18n in your plugin
<?php
// Loading a Text Domain
load_plugin_textdomain( 'plugin-name', false, 'plugin-dir'
);
<h2><?php echo __( 'Your Ad here', 'plugin-name' ); ?></h2>
<h2><?php _e( 'Your Ad here', 'plugin-name' ); ?></h2>

31. Plugin Activation / Deactivation
Activation and deactivation hooks provide ways to perform actions when
plugins are activated or deactivated.
Add rewrite rules, add
custom database tables, or
set default option values.
Activation
Remove temporary data
such as cache, temp files and
directories.
Deactivation

32. Plugin Activation / Deactivation
<?php
register_activation_hook( __FILE__, 'pluginprefix_function_to_run' );
function pluginprefix_function_to_run() {
// Your code
}
register_deactivation_hook( __FILE__, 'pluginprefix_deactivation' );
function pluginprefix_deactivation() {
// Your code
}

33. Transients API (Cache)
Is a simple way of storing cached data in the
database temporary by giving it a custom name
and a timeframe after which it will expire and be
deleted.

34. Set / update the value in transient.
if ( false === ( $query_results = get_transient( 'special_query_results' ) ) ) {
$query_results = new WP_Query( 'cat=5&tag=tech&post_meta_key=featured' );
set_transient( 'special_query_results', $query_results, 12 * HOUR_IN_SECONDS );
}
// Use the data like you would have normally...
print_r($query_results);

35. Security Notes

36. Nonces
// Without nonce
http://example.com/wp-admin/post.php?post=123&action=trash
// With nonce
http://example.com/wp-admin/post.php?post=123&action=trash&_wpnonce=b192fc4204
Nonces are generated numbers used to verify origin and
intent of requests for security purposes. Each nonce can only
be used once.

37. Sanitizing User Data
sanitize_sql_orderby()
sanitize_text_field()
sanitize_textarea_field()
sanitize_title()
sanitize_title_for_query()
sanitize_title_with_dashes()
sanitize_user()
sanitize_email()
sanitize_file_name()
sanitize_html_class()
sanitize_key()
sanitize_meta()
sanitize_mime_type()
sanitize_option()
Checks for invalid
UTF-8
Converts single
< characters to
entity
Strips all HTML
tags
Remove line
breaks, tabs and
extra white space

38. Blocking direct access
<?php
defined( 'ABSPATH' ) or die( 'No script kiddies please!' );
// Your codes...
Prevent direct access provides a simple way to protect your
WordPress PHP files.

39. Ignite
github.com/veronalabs/ignite

40. Options Page

41. Support Namespace
<?php
namespace Ignite;
/**
* Class Option
* @package Ignite
*/
class Option {

42. Clean Structure

43. Installing and Creating Table
WP_List_Table

44. Support WP-REST API

45. Template Functions
use IgniteOption;
/**
* @param $option_name
*
* @return string
*/
function ignite_get_option( $option_name ) {
return Option::get( $option_name );
}

46. Answer Questions!

47. Thank you!
Mostafa Soufi
WordPress: profiles.wordpress.org/mostafas1990
GitHub: github.com/mostafasoufi
Website: soufi.me
Email: mostafa@veronalabs.com
Getting this slide: bit.ly/WP-ISTANBUL

48. Customer Support
Navid Kashani

49. When hire your first customer
support agent?
One Important Question:

50. Quality in Support

51. So, What can we do?

52. Focus on your support from day one
Because:
● Support is very expensive
● It can reduce your cost especially in future
● Learn more about your customers & the problem you want
to solve

53. Do we need to hire a support
person from day one?
NO!

54. ● Improve your support process
● Solve your support request before they are born
So, What should we do?

55. Step One: Set the Metrics
Good for start:
● Response Time
● Response Quality

56. Step Two: One Channel
If you have multiple channels of support, integrate them in a
central hub and grant access to your entire team to get an idea
of the latest issues and user's pains. One of the best services
for this is Slack!

57. Solve your support request
before they are born

58. Categorize your support requests

59. User Experience based on
Customer Support

60. Example

63. Make Documentation
● Documents
● FAQs
● Videos
● Videos
● Videos
useloom.com

64. When hire your first customer
support agent?
Question:

65. When you are ready!
Answer:
Make sure the cost of support doesn’t kill your product or
your team

66. One More Thing

67. Your first support person should create Docs,
FAQ, Videos, based on support requests

68. Thank you!
Navid Kashani
WordPress: profiles.wordpress.org/kashani
GitHub: github.com/navidkashani
Website: navid.kashani.ir
Email: navid@veronalabs.com
Getting this slide: bit.ly/WP-ISTANBUL