Professional WordPress Plugin Development. Brad Williams

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      <?php $email_to = '[email protected]'; $email_subject = 'Plugin email example'; $email_message = 'How do you like my new plugin?'; wp_mail( $email_to, $email_subject, $email_message ); ?>

      As you can see, sending an email in WordPress couldn't be easier. Unless your plugin needs some customized emailing functionality, you don't need to re‐create this function from scratch. Using this function also ensures the widest adoption for sending emails from WordPress because you use the built‐in function.

      Using the available built‐in features of WordPress can greatly reduce the time to develop a plugin. Another advantage of not reinventing the wheel is that this approach more often than not will allow for your plugins to work across a greater number of servers and setups, thereby maximizing compatibility. Don't reinvent the wheel with features that already exist in WordPress.

      Separating Plugins and Themes

      A plugin can take control of the rendering process; therefore, the plugin can become a “theme.” Similarly, a theme can have plugin functionality included. Because of this, the difference between the two can sometimes become blurred, so why not just include your plugin code directly in a theme? This is a common question and one that can have a few different answers.

      Should themes include plugin functionality? The short answer is no. The primary reason for this is because plugins are meant to add features and functionality to WordPress, regardless of the theme used. This creates a nice separation between your website design and the functionality of your website. The reason this separation is needed is so your theme is not directly tied to the functionality required. WordPress is built so that you can easily change your design, or theme, at any point with just a couple clicks. If all plugin functionality existed in your theme and you switched themes, you will have lost all that functionality you required.

There is also a strong argument that certain features should be included in a theme. A common feature most themes include is breadcrumb navigation. This feature could certainly exist in a plugin, and there are many plugins available for this, but it makes more sense to include this navigation‐centric feature in the theme.

      Easy Updates

      WordPress makes it easy to update a plugin to the latest version. Every plugin installed from the WordPress.org Plugin Directory alerts you when a new version of the plugin has been released. Updating the plugin is as simple as clicking the update notification listed just below the plugin details on the Plugin screen of your WordPress Dashboard.

      Plugins not installed from the Plugin Directory can also be updated using the auto‐update functionality of WordPress. This is the method that premium plugins, specifically plugins that are sold on third‐party websites outside of the Plugin Directory, push out updates to their plugins. The plugin author must define where WordPress can download the latest version, and WordPress will take care of the rest. If the plugin author doesn't define this location, you must manually update the plugin.

      Keeping plugins updated is an important part of keeping your website free from security vulnerabilities and bugs.

      Easier to Share and Reuse

      Plugins are easy to share with others. It's much easier to share a plugin than tell someone to modify specific lines of code in your theme or WordPress. Using plugins also makes it easy to use the same functionality across multiple sites. If you find a group of plugins that you like, you can easily install them on every WordPress website you create.

      Plugin Sandbox

      When you activate a broken plugin in WordPress, it won't break your site. If the plugin triggers a fatal error, WordPress automatically deactivates the plugin before it has a chance to wreak havoc. This fail‐safe feature makes it less risky when activating and testing new plugins. Even if the plugin does cause a white screen of death (error message), you can easily rename the plugin folder directly on your web server, and WordPress deactivates the plugin. This makes it impossible for a rogue plugin to lock you out of your own site because of an error.

      On the other hand, if you were to hack the WordPress Core, you could cause fatal errors that would crash your website. This can also include causing unrecoverable damage to WordPress.

      Plugin Community

      A huge community is centered around plugin development, sharing knowledge and code, and creating amazing plugins. Getting involved in the community is a great way to take your plugin development skills to the next level. Chapter 16, “The Developer Toolbox,” covers many of these resources.

INSTALLING AND MANAGING PLUGINS

All plugin management in WordPress happens on the Plugins screen in the WordPress Dashboard. The menu shown in Figure 1‐2 is available only to administrators in WordPress, so non‐administrators cannot see this menu. If you use the Multisite feature of WordPress, the Plugins menu is hidden by default. You need to enable the menu using My Sites ➪ Network Admin ➪ Settings.

FIGURE 1‐2: Plugins menu

      Installing a Plugin

      WordPress features three different methods for installing a new plugin. Your server setup dictates which method is the best to use.

      The first method uses the built‐in auto‐installer. This method enables you to search the Plugin Directory on WordPress.org directly from the Dashboard of your WordPress website. Simply visit Plugins ➪ Add New from your WordPress Dashboard to search for a plugin. After you find a plugin to install, click the Install Now button, and the plugin automatically downloads and installs.

The second method uses the zip uploader. Zipped plugin files can be uploaded, extracted, and installed by WordPress. To use this method, click the Upload Plugin button at the top of the Add Plugins page. Click the Choose File button and select the plugin zip file you want to install. After you select the plugin, click the Install Now button, as shown in Figure 1‐3.

FIGURE 1‐3: Install Now button

      The third and final method to install a plugin in WordPress uses Secure (or SSH) File Transfer Protocol (SFTP). Using SFTP involves simply connecting to your web server using an SFTP client and manually uploading the plugin to your WordPress installation. To use this method, upload the uncompressed plugin folder or file to the wp‐content/plugins directory on your web server.

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