Uninstall and cleanup hooks in Wordpress - Step-by-Step Execution

Concept Flow - Uninstall and cleanup hooks

Plugin Installed

↓

Plugin Activated

↓

Plugin Used

↓

User Chooses to Uninstall

↓

Trigger uninstall.php

↓

Run uninstall hook

↓

Cleanup Database and Files

↓

Plugin Fully Removed

This flow shows how WordPress runs uninstall hooks to clean up plugin data when a user uninstalls a plugin.

Execution Sample

Wordpress

<?php
// uninstall.php
if (!defined('WP_UNINSTALL_PLUGIN')) {
    exit;
}
// Remove options
delete_option('my_plugin_option');
// Remove custom tables
global $wpdb;
$wpdb->query("DROP TABLE IF EXISTS {$wpdb->prefix}my_plugin_table");

This code runs when the plugin is uninstalled to delete saved options and custom database tables.

Execution Table

Step	Action	Check	Result	Effect
1	Check if WP_UNINSTALL_PLUGIN is defined	WP_UNINSTALL_PLUGIN defined?	Yes	Continue uninstall
2	Delete option 'my_plugin_option'	Option exists?	Yes	Option removed from database
3	Drop custom table 'wp_my_plugin_table'	Table exists?	Yes	Table deleted from database
4	Finish uninstall script	No more cleanup	Done	Plugin data fully cleaned

💡 Uninstall script ends after cleaning options and tables

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
WP_UNINSTALL_PLUGIN	defined	defined	defined	defined
my_plugin_option	exists	deleted	deleted	deleted
wp_my_plugin_table	exists	exists	deleted	deleted

Key Moments - 2 Insights

Why do we check if WP_UNINSTALL_PLUGIN is defined?

This check ensures the uninstall script runs only when WordPress triggers uninstall, preventing direct access. See execution_table step 1.

What happens if the option or table does not exist?

The delete_option and DROP TABLE commands safely do nothing if the data is missing, so uninstall continues without errors. See execution_table steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 2?

A The plugin option is deleted from the database

B The uninstall script exits immediately

C The custom table is dropped

D WP_UNINSTALL_PLUGIN is undefined

💡 Hint

Check the 'Action' and 'Effect' columns in execution_table row 2

At which step does the uninstall script confirm it is running inside WordPress uninstall?

A Step 4

B Step 3

C Step 1

D Step 2

💡 Hint

Look at the 'Check' column in execution_table row 1

If the custom table does not exist, what changes in the execution table?

A Step 2 result changes to 'No'

B Step 3 result changes to 'No', and table is not deleted

C Step 4 is skipped

D Uninstall script exits at step 1

💡 Hint

Refer to execution_table step 3 'Check' and 'Result' columns

Concept Snapshot

WordPress uninstall hooks run when a plugin is removed.
Use uninstall.php with a check for WP_UNINSTALL_PLUGIN.
Delete options and custom tables to clean data.
This prevents leftover data after uninstall.
Always secure uninstall.php from direct access.

Full Transcript

When a WordPress plugin is uninstalled, WordPress runs the uninstall.php script if it exists. This script must check if the constant WP_UNINSTALL_PLUGIN is defined to confirm it is running during uninstall and not accessed directly. The script then deletes plugin options using delete_option and removes custom database tables with SQL DROP TABLE commands. This cleanup ensures no leftover data remains after the plugin is removed. The execution table shows step-by-step how the uninstall script checks conditions and deletes data safely. Variables like WP_UNINSTALL_PLUGIN, plugin options, and tables change state during the process. Key points include the importance of the WP_UNINSTALL_PLUGIN check and safe deletion commands that do nothing if data is missing. The visual quiz tests understanding of these steps and their effects.