WordPress Plugins are very elaborate and would require significant programming expertise to develop. In this session details are shared on Files/Folder Structure, Naming Conventions/ Coding Practices,Improving Form,Database Interaction,Loading CSS, JavaScript, Image Files and Making Proper Ajax Calls etc.

1. Wordpress Plugin
Development Tips
Chittaranjan Pattnaik
Mindfire Solutions

2. Agenda

Files/Folder Structure

Naming Conventions/ Coding Practices

Improving Form

Database Interaction

Loading CSS, JavaScript, Image Files

Making Proper Ajax Calls

Miscellaneous

Conclusion

References

3. Files/Folder Structure



Always use – (hyphen) as a separator for file and
folder names.
Files should be named descriptively using lowercase
letters.
Have dedicated folders for files like configuration,
javascript, css, images etc.
Ex:
mfs-mailbox
mfs-mailbox/scripts/mfs-mailbox.js

4. Naming Conventions/ Coding Practices
• Follow wordpress coding standards and use proper
comments.
• Have consistent coding and use proper file and
function headers.
Ex:
Plugin Name: MFS Mailbox
Description: This plugin plugin will allow registered users to send mail(s)
to other registered users.
Version: 1.1
Author: Mindfire Solutions
Author URI: http://www.mindfiresolutions.com/

5. Naming Conventions/ Coding Practices
• Always use your plugin name as a prefix to all the
functions, variables you define. Adopting OOPS
concept will better serve this purpose.
Ex:
function mfs_mailbox_send_mail( $mail_data ) {
}
class Mfs_Mailbox {
function send_mail ( $mail_data ) {
}
}
Contd…

6. Naming Conventions/ Coding Practices
• Dependency: If your plugin depends on any other
plugin(s), then always check for existence of such
plugin(s).
Ex:
Let’s say the parent plugin has a class, then first check for existence of the
class. If it DOES NOT exist, then show some message.
if (!class_exists(' Wordpress_Mail ')) {
echo __('Wordpress mail plugin must be installed before using this
plugin ', 'mfs-mailbox');
exit;
}
Contd…

7. Naming Conventions/ Coding Practices
• Separate Plugin Admin Code: If you want to have any
code/functionality meant only for admin end, then you
can check for admin section by using is_admin and
have the respective code inside that block.
Ex:
if ( is_admin() ) {
// Add the functionality for the admin end
} else {
// Add the functionality for the frontend
}

8. Naming Conventions/ Coding Practices
• DO NOT make unnecessary repetitive function calls.
Ex:
Let’s say you have to repeatedly cross check whether a user is
logged in or not. Wordpress has a function is_user_logged_in
to verify this. Instead of calling this function again and again,
you can store this function return value in a variable and
compare that variable instead.
• DO NOT use end php tag.

9. Improving Form
• Permalink: Use proper action attribute, DO NOT
hardcode with specific type page url. Use
get_permalink method to collect the proper url
irrespective of permalink settings.
Ex:
site_url/?page_id=10
site_url/process-mail
Preferred Approach
get_permalink(10);

10. Improving Form
• Nonce: Always use nonce for security purpose and
validate with this nonce first before processing the form
data.
Ex:
wp_nonce_field('mfsbox', 'mfs_mailbox_nonce');
if (!wp_verify_nonce($_POST['mfs_mailbox_nonce'], 'mfsbox')) {
// Invalid access
} else {
// Process form data
}

11. Database Interaction
• Database version: Record database version for each
version of the plugin you have. You can cross check
with this version in case you need to make any
modifications to the related tables in the plugin’s
updated version.
Ex:
$mfs_mailbox_db_version = '1.1';
if (get_option('mfs_mailbox_db_version') != $mfs_mailbox_db_version) {
// Update tables
}
update_option('mfs_mailbox_db_version', $mfs_mailbox_db_version);

12. Database Interaction
• Table Prefix: Always use table prefix for interacting
with wordpress tables.
Ex:
Let’s say your plugin uses a table called wp_mfs_mailbox where wp_ is
the table prefix for your wordpress installation. It’s always good to refer to
this table as {$wpdb->prefix}mfs_mailbox.
"SELECT * FROM {$wpdb->prefix}mfs_mailbox";

13. Database Interaction
• Proper data: Use prepared statements for database
operations. You should also sanitize the data to the
maximum extent.
Ex:
$admin_mails = $wpdb->get_results("SELECT * FROM
{$wpdb->prefix}mfs_mailbox WHERE mail_status = 'publish' AND
mail_author = 1");
Preferred Approach
$admin_mails = $wpdb->get_results($wpdb->prepare("SELECT * FROM
{$wpdb->prefix}mfs_mailbox WHERE mail_status = %s AND
mail_author = %d", 'publish', 1));

14. Loading CSS, JavaScript, Image Files
• First register your javascript files using
wp_register_script.
• Use wp_localize_script to declare any javascript
variables which you need.
• Use wp_enqueue_script to load your script files.
Ex:
wp_register_script( 'mfs_mailbox_script', plugins_url( 'scripts/mfsmailbox.js', __FILE__ ), array('jquery') );
wp_localize_script( 'mfs_mailbox_script', 'mfs_ajax', array('url' =>
admin_url( 'admin-ajax.php' )));
wp_enqueue_script( 'mfs_mailbox_script' );
Contd…

15. Loading CSS, JavaScript, Image Files
• Prefer using jQuery instead of $.
• If you are using any jQuery event function, prefer using
live function for handling such events.
Ex:
jQuery('.mfs_link').click(function(){
});
Preferred Approach
jQuery('.mfs_link').live('click', function(){
});
Contd…

16. Loading CSS, JavaScript, Image Files
• We have similar functions for loading css files like
wp_enqueue_style to load css files.
Ex:
wp_register_style( 'mfs_mailbox_style', plugins_url('css/mfs-mailbox.css',
__FILE__) );
wp_enqueue_style( 'mfs_mailbox_style' );
• Always use plugins_url function to get the correct url
for javascript, css, image files. This function is really
handy when SSL is enabled.
Ex:
echo "<img src='" . plugins_url( 'images/pixel.gif', __FILE__ ) . "' />";

17. Loading CSS, JavaScript, Image Files
• Prefer loading javascript and css files in footer so that
they will load after all javascript and css files get
loaded. This is helpful if there is any dependency
among the files.
Ex:
wp_register_script( $handle, $src, $deps, $ver, $in_footer );
wp_register_script( 'mfs_mailbox_script', plugins_url( 'scripts/mfsmailbox.js', __FILE__ ), array('jquery'), '1.1', true );

18. Making Proper Ajax Calls
• DO NOT load wp-config or wp-load file for processing
your data inside the ajax files.
• DO NOT refer to the url of the file for processing ajax
calls.
• Call to admin-ajax file with proper action for carrying
out ajax operation. Use admin_url function to find
proper url for this.
• Always attach nonce to each ajax call even if you are
making calls from admin end.

19. Making Proper Ajax Calls
Ex:
$nonce = wp_create_nonce('mfs_mailbox_nonce');
Create the url to the admin-ajax file with proper action and nonce.
$ajax_mail_link = admin_url('admin-ajax.php?
action=mfs_mailbox_process&task=send_mail&nonce=' . $nonce);
Attach a function which will be called for the above action.
add_action('wp_ajax_mfs_mailbox_process', 'mfs_mailbox_send_mail');

20. Making Proper Ajax Calls
Ex:
if (!wp_verify_nonce( $_REQUEST['nonce'], 'mfs_mailbox_nonce')) {
// Invalid access
} else {
// Valid access, so go ahead with processing the data
}

21. Miscellaneous
• Make your plugin capable of working in a multisite
environment.
• Always use language files so that it can easily be
translated to other languages.
Ex:
load_plugin_textdomain( 'mfs-mailbox', false, 'mfs-mailbox/lang' );
Here is how you will write to show the message which can be later
translated.
echo __( 'Mail sent successfully', 'mfs-mailbox' );

22. Miscellaneous
• Have a proper readme.txt file having all the details
about the plugin specifically when you want to submit
this to wordpress plugin repository.
• Always have FAQ section for your plugin so that users
will get answers to some basic questions.
• You can also add screenshots to showcase the
functionalities those are provided by your plugin.

23. Conclusion
Your plugin will work even if you do not follow the
above points to the full extent. But when we consider
ourselves as professional wordpress developers, we
should take each and every possible approach to write
better plugin code. You should adopt the best practices
and take pride in whatever you develop.

24. References
• http://codex.wordpress.org/Getting_Started_with_WordPr
• http://codex.wordpress.org/WordPress_Coding_Standards