wp-fix-plugin-does-not-exist-notices/.wiki/How-It-Works.md

How It Works

This page explains the technical details of how the "Fix 'Plugin file does not exist' Notices" plugin works to identify and clean up orphaned plugin references in your WordPress installation.

Understanding the Problem

When a plugin is properly deactivated and deleted through the WordPress admin interface, WordPress removes all references to that plugin from the database. However, if a plugin is deleted by directly removing its files (via FTP, SSH, or file manager), WordPress doesn't know that the plugin has been removed.

As a result, WordPress continues to try to load the plugin during initialization, but since the plugin files no longer exist, it generates a "Plugin file does not exist" notice in the admin dashboard. These notices can be confusing and annoying, especially for non-technical users.

The Solution

The "Fix 'Plugin file does not exist' Notices" plugin addresses this issue by:

1. Scanning the WordPress database for references to plugins
2. Checking if the referenced plugin files actually exist
3. Adding missing plugins to the plugins list with a "Remove Notice" action link
4. Allowing you to safely clean up invalid plugin references directly from the plugins page

Technical Implementation

Scanning Process

The plugin scans the following locations in the WordPress database:

1. Options Table:

   • active_plugins option: Contains a serialized array of active plugins
   • active_sitewide_plugins option (for multisite): Contains a serialized array of network-activated plugins
   • recently_activated option: Contains a serialized array of recently deactivated plugins

2. Site Options Table (for multisite):

   • active_sitewide_plugins site option: Contains a serialized array of network-activated plugins

3. User Meta Table:

   • wp_user_settings user meta: May contain references to plugins in user-specific settings

Validation Process

For each plugin reference found, the plugin:

1. Extracts the plugin file path (e.g., plugin-name/plugin-file.php)
2. Constructs the full path to the plugin file (e.g., /wp-content/plugins/plugin-name/plugin-file.php)
3. Checks if the plugin file exists using PHP's file_exists() function
4. If the file doesn't exist, marks the reference as orphaned

Cleanup Process

When cleaning up orphaned references, the plugin:

1. Retrieves the current value of the relevant option or meta
2. Deserializes the value (if it's serialized)
3. Removes the orphaned references from the data structure
4. Reserializes the value (if necessary)
5. Updates the option or meta with the new value

Safety Measures

To ensure safety and prevent data corruption, the plugin:

1. Validates all data before and after modification
2. Uses WordPress core functions for database operations when possible
3. Implements proper error handling and logging
4. Provides undo capabilities through database backups
5. Follows WordPress coding standards and best practices

Integration with WordPress

The plugin integrates with WordPress in the following ways:

Admin Integration

• Integrates directly with the WordPress plugins page
• Adds missing plugins to the plugins list with "(File Missing)" indicator
• Provides a "Remove Notice" action link for each orphaned plugin reference
• Displays success/error messages after cleanup operations
• Adds an "Update Source" link to select your preferred update source

Modal Interface

• Provides a modal dialog for selecting the update source
• Offers three options: WordPress.org, GitHub, and Gitea
• Saves the selected update source preference
• Ensures the plugin checks for updates from the selected source

Git Updater Integration

• Integrates with the Git Updater plugin for updates from GitHub and Gitea
• Provides proper plugin headers for Git Updater compatibility
• Ensures correct version display in plugin details popup

Performance Considerations

The plugin is designed with performance in mind:

• Only runs on the plugins page where it's needed
• Performs scans efficiently to minimize database queries
• Uses WordPress core functions for database operations
• Implements proper caching for plugin information
• Has minimal impact on admin page load times

Security Considerations

The plugin follows security best practices:

• All user inputs are properly sanitized and validated
• Database queries are prepared and escaped to prevent SQL injection
• Capability checks are performed to ensure only authorized users can perform actions
• Nonce verification is used to prevent CSRF attacks

Compatibility

The plugin is designed to be compatible with:

• All WordPress versions from 5.0 and up
• Single-site and multisite WordPress installations
• Various hosting environments and server configurations
• Common caching and optimization plugins
• Popular security plugins