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1. 1. What is the essential difference between a WordPress action and a filter?

   Choose the statement that correctly describes the contract expected by WordPress.

   What is the essential difference between a WordPress action and a filter?

   There is no functional difference between them. An action performs a task; a filter modifies and returns a value. An action must always return a value; a filter returns nothing. Filters work only inside themes.
   Hint

   Ask yourself whether the received value must continue through the execution chain.

2. 2. How does hook priority affect callbacks attached to the same hook?

   Assume all callbacks are valid and registered.

   How does hook priority affect callbacks attached to the same hook?

   Priority applies only to filters, not actions. Priority changes how many arguments WordPress passes. Higher numeric priorities always run earlier. Lower numeric priorities run earlier.
   Hint

   Compare numeric priority values.

3. 3. Which checks belong in a save_post metabox handler?

   Select all generally appropriate safeguards.

   Which checks belong in a save_post metabox handler?

   Check the user capability for the post. Trust every value in $_POST because the request came from wp-admin. Verify the metabox nonce. Handle or skip autosaves deliberately.
   Hint

   Consider request intent, autosaves, and authorization.

4. 4. Which hook is appropriate when a plugin must initialize after all active plugins have loaded?

   Which hook is appropriate when a plugin must initialize after all active plugins have loaded?

   wp_loaded plugins_loaded after_setup_theme init
   Hint

   Think about when every active plugin file has been included.

5. 5. What happens if a filter callback forgets to return the filtered value?

   What happens if a filter callback forgets to return the filtered value?

   The filter becomes an action PHP always throws a fatal error Later callbacks may receive null or an unintended value WordPress automatically returns the original value
   Hint

   Actions may ignore return values; filters may not.

6. 6. What must match when removing a callback with remove_action()?

   What must match when removing a callback with remove_action()?

   The accepted argument count Only the hook name The hook name, callback, and priority used when it was added Only the callback name
   Hint

   A callback registered at priority 20 cannot be removed as though it used priority 10.

7. 7. What does the accepted_args parameter of add_filter() control?

   What does the accepted_args parameter of add_filter() control?

   How many times the callback runs The callback priority How many values WordPress passes to that callback How many callbacks may use the hook
   Hint

   It describes callback input, not execution order.

8. 8. Which function can check whether a particular action is currently executing?

   Which function can check whether a particular action is currently executing?

   current_filter() doing_action() did_action() has_action()
   Hint

   Distinguish currently running from already fired.

9. 9. What does has_filter() return when a specific callback is registered?

   What does has_filter() return when a specific callback is registered?

   Its priority The hook name The number of accepted arguments The callback result
   Hint

   The return value must distinguish priorities.

10. 10. What does did_action( $hook_name ) report?

    What does did_action( $hook_name ) report?

    The last callback result Whether the action is running now How many times the action has fired How many callbacks are registered
    Hint

    It is a counter, not a boolean-only check.

11. 11. Inside a shared callback, which function identifies the hook currently being processed?

    Inside a shared callback, which function identifies the hook currently being processed?

    current_filter() did_action() get_current_hook() doing_filter() only
    Hint

    Useful when one callback handles several hooks.

12. 12. What is the safest first check before modifying the public main query in pre_get_posts?

    What is the safest first check before modifying the public main query in pre_get_posts?

    Flush rewrite rules Confirm ! is_admin() and $query->is_main_query() Check is_singular() globally Call query_posts()
    Hint

    Avoid changing admin and secondary queries.

13. 13. Why is init commonly used for rewrite-related registrations?

    Why is init commonly used for rewrite-related registrations?

    It runs only once Post types and taxonomies must exist before rewrite parsing is finalized It runs after template output It automatically flushes rules
    Hint

    Registration and flushing are different operations.

14. 14. Which task is most suitable for the shutdown hook?

    Which task is most suitable for the shutdown hook?

    Changing template hierarchy Enqueueing a stylesheet Final lightweight cleanup or logging after the response lifecycle Registering a post type
    Hint

    It is late in the request.

15. 15. When is do_action_ref_array() useful?

    When is do_action_ref_array() useful?

    When hook arguments are already stored in an array and references matter To create an AJAX nonce To remove all filters When no callbacks exist
    Hint

    Compare it with call_user_func_array().

16. 16. Why should attaching a callback to the special all hook be approached carefully?

    Why should attaching a callback to the special all hook be approached carefully?

    It runs for every hook and can create major overhead It works only in multisite It disables priorities It cannot receive arguments
    Hint

    Broad instrumentation has a cost.