A talk by Laxman Kasula, Ingenious IT.

1. WordPress Nepal
WordPress Meetup # 13

2. Laxman Kasula
PHP Developer (Primarily focused on
WordPress) @ Ingenious IT Pvt. Ltd.
e-mail: laxman.kasula@gmail.com

3. Simple Contact-us Plugin Development

4. Objective
• To develop a simple plugin that would
motivate to develop the complex plugin.

5. WordPress Plugin
• A single file or a group of files inside a folder
to add features to WP.
• Put the plugin into plugins folder (wp-
content/plugins) and activate from plugins
menu in the backend.
• WordPress Plugins Repository:
http://wordpress.org/extend/plugins/

6. Plugin Development Good Practices
1. Organize Files
• main plugin file and uninstall.php in the folder
and all others in subfolders like js, css,
includes, images …
2. Prefix Everything
• uniquely prefix every variables and functions.

7. Lets start developing the plugin
wpnepal-contacts

8. A. Prefix Used: wpnepal-contacts
B. Files Organization
1. wpnepal-contacts.php (primary file)
2. uninstall.php
3. css
• wpnepal-contacts-form.css
4. js
• wpnepal-contacts-custom-script.js
• jquery-ui-1.8.18.custom.min.js
• jquery.validate.js
• gen_validatorv31.js
5. includes
• wpnepal-contacts-table.php
• wpnepal-contacts-form.php
• wpnepal-general-functions.php
• wpnepal-admin-settings.php
• captcha_code_file.php
• monofont.ttf

9. 1. Create the plugin defination header
/* Plugin Name: WPNepal Contacts Form */
2. activate, deactivate and uninstall
a. activation: register_activation_hook()
--- check the wordpress version
--- create the table to store contacts information
b. deactivation: register_deactivation_hook()
c. uninstallation:
i. uninstall.php OR
ii. register_uninstall_hook()
--- drop the contacts info table

10. 3. Action Hooks
• to fire a function at a specific point.
• ‘plugins_loaded’ action hook: load_plugin_textdomain()
4. Accessing the plugin functionality
1. Widgets
2. Call functions in templates
3. shortcodes
---[wpnepal_contacts_form] with add_shortcode()
5. Include the Contact Form

11. 6. Add the css and js files to the page
• ‘template_redirect’ action
• wp_enqueue_style() and wp_enqueue_script()
• wp_localize_script()
--- all ajax request are sent to admin-ajax.php (
wp-admin directory ).
--- pass dynamic variable to the js file ( path of
admin-ajax.php and the nonce value ).

12. 7. NONCE (Number used ONCE)
• Specific to:
– One WP user
– one action (delete, update, edit...)
– one object (a post, a link, a plugin setting)
– one time frame of 24 hours
• Example: ‘action=process-wpnepal-contacts-
form&wpnepal_contacts_form_nonce=eb587a5939’
--- nonce value ‘eb587a5939’ is valid for only 24
hours to only action ‘process-wpnepal-contacts-
form‘ and only for only you.
• WP verifies if the nonce meets all the criterias before
processsing the actions.

13. 8. Process the form action
• process the action parameter using 2 ajax actions
1. wp_ajax_$action
--- hooks functions if the user is logged in.
2. wp_ajax_nopriv_$action
--- hooks functions if the user is not logged in and
has no privilege.
• verify nonce: wp_verify_nonce()
• if verified, sanitize and validate the obtained
data.
• insert into the table: $wpdb->insert()
• send an email: wp_mail()

14. 9. Filter
• to manipulate the output of the content.
• Html email: ‘wp_mail_content_type’ filter
using add_filter()

15. Improvements: Add Settings Page

16. 10. Adding Settings Page to WP Backend
• Menus
– Action: ‘admin_menu’
add_menu_page()
add_submenu_page( )
add_plugins_page()
add_theme_page()
• Handling Options
– Use Options API and Settings API to properly save the
options in a WP manner.
– Options API:
add_option(),
update_option(),
get_option(),
delete_option()

17. 11. Settins API
• 3 Components
1. Fields
--- individual options: textbox, radio, checkbox
--- add_settings_field()
2. Sections
--- logical group of fields
--- add_settings_section()
3. Settings
--- ( Fields + Sections )
--- register_setting()
• Rendering Options to the Page
– settings_fields(): takes care of rendering several security
measures for the options form.
– do_settings_sections(): actually renders the options to the
page.

18. 12. Actions Encountered
– init, admin_init
– plugins_loaded
– template_redirect
– wp_print_styles, wp_print_scripts
– wp_ajax_, wp_ajax_nopriv_
– admin_menu
13. Filters Encounterd
– wp_mail_content_type
14. Functions Encounterd
– plugin_dir_path(), plugin_dir_url()
– register_activation_hook(), deactivate_plugins(), register_deactivation_hook()
– get_bloginfo()
– add_shortcode()
– load_plugin_textdomain()
– is_page()
– wp_enqueue_style,() wp_enqueue_script(), wp_localize_script()
– wp_create_nonce(), wp_verify_nonce()
– add_option(), get_option()
– Is_email(), wp_mail()
– add_menu_page()
– add_settings_section(), add_settings_field(), register_setting()
– settings_fields(), do_settings_sections()
– dbDelta()

19. Thanks !!!

20. Questions ???