Plugins are separate files of code that extend WordPress in any way imaginable by interacting with the WordPress API. You can add functionality to WordPress without modifying any core code files. A plugin can be as simple or as complex as needed for the job.
Currently more than 7,500 plugins are listed in the official plugin directory and even more are available across the Internet. Plugins are a key component in customizing WordPress to function exactly as you like without altering the core WordPress code. This section is where you install, configure, and manage all plugins across your web site.
A plugin can accomplish just about any functionality imaginable. Most standard CMS tasks can be accomplished via a plugin. If you are looking for a specific feature in WordPress, the first place to start is by searching the plugin directory at WordPress.org.
You manage plugins under the Plugins O Installed SubPanel on your dashboard. WordPress lists all plugins currently located in your wp-content/plugin directory on your web server. Plugins can be activated, deactivated, and deleted from the plugin administration page. Each plugin lists the plugin name, description, and author information including the plugin site. The plugin site is typically the best resource for plugin-specific information and support.
You can filter which plugins are shown by using the filter links across the top of the page. You can also search plugins using the keyword search box at the top right. The Upgrade Available filter is a quick overview of which plugins have an upgrade available and need attention.
To install a plugin on your web site, you can use the same three methods as you would to install a theme: the Auto Installer, Zip Upload, or FTP. Once a plugin has been uploaded to WordPress using one of these three methods, it will appear under Plugins O Installed SubPanel. Here you can activate, deactivate, or delete the new plugin. Once a plugin is placed in the wp-content/plugins directory it automatically displays on your Plugins SubPanel.
If a plugin is removed from the plugins directory on your web server, it is automatically deactivated in WordPress. This is especially handy if a rogue plugin breaks your web site and you are locked out with error messages or the dreaded white screen of death (causing WordPress to go into an infinite loop or otherwise never finish executing some PHP code). Also, if you remove or rename the offending plugin, it will be deactivated in WordPress.
WordPress comes with a built-in plugin upgrade feature. This makes upgrading your plugins easier than ever. When a plugin upgrade is available, a notice appears alerting you about the new version under the Plugins O Installed SubPanel. A notice next to the Plugins SubPanel link on the Admin Menu also appears showing a number circled in red. That is the number of plugins with an upgrade available. The update notice displays links to view the new version details and to upgrade automatically. The upgrade notice is triggered when a new version of a plugin installed on your server has been uploaded to the official plugin directory at WordPress.org.
Clicking the View Version Details link opens a Thickbox overlay showing you the plugins detail page from WordPress.org. From here you can view the plugin description, installation instructions, and a changelog. The changelog features a version history showing you exactly what the new version does. This can help you determine whether the plugin features a security vulnerability fix or new features. The changelog is not a requirement for plugins, so the changelog tab may not exist on all plugins.
Clicking the Upgrade Automatically link starts the plugin upgrade process. If your web host supports automatic upgrade, the upgrade process begins immediately. The auto upgrade downloads the latest plugin zip file from WordPress.org, unpacks the plugin, deactivates the plugin, installs the latest version, and then attempts to reactivate the plugin. If everything runs smoothly your new plugin is installed and activated automatically. The automatic upgrade reactivates your plugin only if it was activated before the upgrade. Always remember to back up your plugins before upgrading. In case of an error in the plugin or on your web site you can always revert back to the backup.
If your web host doesn't support the automatic upgrade process, you are prompted to enter your FTP account information to perform the upgrade. This gives WordPress FTP permission to download and install the update plugin on your server. Fill in your web site's Hostname (FTP Server), Username, Password, and whether you are using FTP or FTPS (SSL). Click the Proceed button to start the upgrade process. From here the upgrade process is the same as the auto upgrade.
Just like with themes, WordPress has a built-in plugin editor with syntax highlighting. You can view any plugin source code, but plugin files must be writable before you can save your changes. Remember there is no "undo" button on a browser. There is also no plugin revision history so one bad code edit and you could break the plugin with no way to revert back to the original code.
The editor lists all files associated with a plugin. You can choose which plugin you would like to edit from the drop-down menu in the top-right corner. A documentation lookup feature has also been added, making it easier than ever to quickly look up a function's purpose. This can help you reference the plugin's actions.
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