Plugin header and activation in Wordpress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a WordPress plugin with this header is activated?

Consider this plugin header in a PHP file placed in the WordPress plugins folder. What will WordPress do when this plugin is activated?

/*
Plugin Name: Simple Logger
Description: Logs a message on activation.
Version: 1.0
Author: Dev
*/

register_activation_hook(__FILE__, function() {
    error_log('Simple Logger activated');
});

Wordpress

/*
Plugin Name: Simple Logger
Description: Logs a message on activation.
Version: 1.0
Author: Dev
*/

register_activation_hook(__FILE__, function() {
    error_log('Simple Logger activated');
});

A WordPress will display 'Simple Logger activated' as a message on the admin dashboard after activation.

B WordPress will log 'Simple Logger activated' to the PHP error log when the plugin is activated.

C The plugin will fail to activate because register_activation_hook cannot be used inside the plugin file.

D Nothing happens because the activation hook is not properly registered.

💡 Hint

Think about what register_activation_hook does and where it runs.

The register_activation_hook function registers a callback that runs only once when the plugin is activated. Here, it writes a message to the PHP error log. It does not display messages in the admin dashboard automatically.

📝 Syntax

intermediate

Identify the correct plugin header syntax

Which of the following plugin headers is correctly formatted so WordPress recognizes it as a valid plugin?

A

/*
Plugin Name: My Plugin
Description: Does something useful
Version: 1.0
Author: Me
*/

B

// Plugin Name: My Plugin
// Description: Does something useful
// Version: 1.0
// Author: Me

C

<!-- Plugin Name: My Plugin -->
<!-- Description: Does something useful -->
<!-- Version: 1.0 -->
<!-- Author: Me -->

D

# Plugin Name: My Plugin
# Description: Does something useful
# Version: 1.0
# Author: Me

💡 Hint

WordPress plugin headers must be inside a PHP comment block at the top of the main plugin file.

WordPress expects the plugin header inside a PHP block comment (/* ... */) at the top of the plugin file. Other comment styles or HTML comments are not recognized.

🔧 Debug

advanced

Why does this activation hook not run?

A developer wrote this plugin code but the activation hook never runs. Why?

/*
Plugin Name: Test Plugin
*/

function activate_test_plugin() {
    error_log('Activated');
}

register_activation_hook('test-plugin.php', 'activate_test_plugin');

Wordpress

/*
Plugin Name: Test Plugin
*/

function activate_test_plugin() {
    error_log('Activated');
}

register_activation_hook('test-plugin.php', 'activate_test_plugin');

A The function activate_test_plugin is missing a required parameter.

B The plugin header is missing the Version field, so activation hooks don't run.

C The error_log function cannot be used inside activation hooks.

D The first argument to register_activation_hook must be __FILE__, not a string filename.

💡 Hint

Check the first argument of register_activation_hook carefully.

register_activation_hook requires the full path to the main plugin file, which is best provided by __FILE__. Passing just the filename string will not work because WordPress cannot locate the file.

❓ state_output

advanced

What is the output after plugin activation and deactivation?

Given this plugin code, what will be logged after activating and then deactivating the plugin?

/*
Plugin Name: Logger Plugin
*/

register_activation_hook(__FILE__, function() {
    error_log('Plugin activated');
});

register_deactivation_hook(__FILE__, function() {
    error_log('Plugin deactivated');
});

Wordpress

/*
Plugin Name: Logger Plugin
*/

register_activation_hook(__FILE__, function() {
    error_log('Plugin activated');
});

register_deactivation_hook(__FILE__, function() {
    error_log('Plugin deactivated');
});

A Only 'Plugin activated' will be logged; deactivation hook does not run automatically.

B Nothing will be logged because error_log is disabled in WordPress plugins.

C The PHP error log will contain 'Plugin activated' after activation and 'Plugin deactivated' after deactivation.

D Both hooks run immediately when the plugin file loads, logging both messages at once.

💡 Hint

Activation and deactivation hooks run only on those specific events.

register_activation_hook runs the callback only when the plugin is activated. Similarly, register_deactivation_hook runs only when the plugin is deactivated. Both write their messages to the PHP error log at those times.

🧠 Conceptual

expert

Why is the plugin header required for activation?

Why does WordPress require a properly formatted plugin header comment block at the top of a plugin file before it can be activated?

A Because WordPress uses the header to identify the plugin's name, version, and author to list it in the admin plugins page.

B Because the header comment block contains PHP code that runs the activation hook automatically.

C Because without the header, WordPress cannot load the plugin's PHP functions into memory.

D Because the header comment block is where WordPress stores the plugin's database connection details.

💡 Hint

Think about how WordPress shows plugins in the admin area.

The plugin header comment block provides metadata WordPress reads to display the plugin in the admin interface. Without it, WordPress does not recognize the file as a plugin and won't allow activation.