Plugin Development

Question 1

function update_option

Answer 1

Used to create or update a new key in wp_options table

Accepts name of key to create or update, and the vale that needs to be stored in it

Question 2

init action hook

Answer 2

Fires after Wordpress finished loading but before any headers are sent
Accepts name of custom function to callback
Good stage to set values needed for the plugin to work, like custom post types and taxonomies.

Question 3

What is a text domain

Answer 3

Unique identifier that helps Wordpress to distinguish between different translations of this plugin.
Domain name should be the name of main plugin file without extension.
Must use dashes, not underscores

Question 4

Function __()

Answer 4

Used to demote text elements that can be translated into other languages.

Question 5

Function register_post_type

Answer 5

Used to register new post type
Should be called within init action hook
Its value is stored wp_posts post_type field
Accepts name of the post type and arguments / settings.

Question 6

admin_menu action hook

Answer 6

Used to add menu pages to admin

Accepts name of the callback function that will be called to create the menu

Question 7

Function add_options_page

Answer 7

Adds submenu item under dashboard > settings
Accepts page title tag, menu item’s anchor text, user capability, slug, callback to output HTML form of the settings page

Question 8

Function get_option

Answer 8

A safe way of getting value of a saved option from wp_options table
Accepts name of the key whose value to retrieve

Question 9

Function _e()

Answer 9

Same as __(), but in addition to making it translatable, outputs the vale to screen

Question 10

Function settings_fields

Answer 10

Accepts name of settings group
Should be called before register_setting functions
Is called inside of options html form
Tells register_setting that once submitted the group name should be matched with group name in register setting! and if matched values should be saved in the right option key.

Question 11

Function esc_attr()

Answer 11

Should be used to sanitize vales of HTML attributes

Question 12

Function sanitize_text_field()

Answer 12

Does the same as esc_atts, but is used for the actual values that come from input tags. Good to use before display and before querying the database.

Question 13

add_meta_boxes action hook

Answer 13

Runs whe edit post screen is loaded

Used to construct custom meta fields for a post

Question 14

Function add_meta_box()

Answer 14

Allows plugin developers to add meta boxes to edit / create post screen
Should be called from add_meta_boxes action hook
Accepts ID attribute name of wrapping element, section heading, callback that prints the HTML form, screen - name of post type, context - section of the page

Question 15

Function get_post_meta

Answer 15

Retrieve post meta fields
Requires ID of the post
Returns either all meta associated with post, or just meta of specific key
Data is pulled from wp_postmeta

Question 16

Function wp_nonce_field

Answer 16

Used to ensure that data sent for saving comes from the actual form and not somewhere else.
Accepts action name that describes what this form does, and nonce name, which can be anything

Question 17

Function selected()

Answer 17

Used in select options, checks two values given, and if they match selected attribute is added.

Question 18

save_post action hook

Answer 18

Runs when a post or a page is created or updated

The callback function gets ID of the last saved post

Question 19

Function get_post_type

Answer 19

Retrieves the post type of the current or given post

Returns a string that matched post_type field of wp_posts table.

Question 20

Function wp_verify_nonce

Answer 20

Checks if data sent comes from the actual site and form, and not somewhere else. Should be passed action and name set earlier by wp_nonce_field.

Question 21

Function array_map()

Answer 21

Accepts call back function that will be applied on each value of the array passed to it, such as sanitize_text_field. Returns array with values sanitized.

Question 22

Function update_post_meta

Answer 22

Queries database
Either creates or updates wp_postmeta table
Accepts post ID, name of the key, and value

Question 23

What is a shortcode

Answer 23

Placeholder you add to content that is replaced by Wordpress with other content. Can be with or without attributes

Question 24

Function add_shortcode

Answer 24

Used to add replace code macros with the actual content

Accepts tag and callback function

Question 25

What’s a widget

Answer 25

Widget is a small program that allows users to easily add plugin info into sidebar or any other widgetized area.

Question 26

widgets_init action hook

Answer 26

Triggered right after all default widgets are built

Question 27

Function wp_parse_args()

Answer 27

Merges user defined arguments into $defaults array, and returns updated array with default keys overwritten.

Question 28

function register_activation_hook

Answer 28

Is run when plugin activated
Says which function to call upon activation
Accepts full path to main plugin file and name of the custom function to run