Developer Workshop: What I Wish I'd Known When I Started

WordPress provides a lot of convenience functions, perhaps too many. All too often, new developers reinvent the wheel, as the cliche goes, when Core already has a function or utility to accomplish the same. Six years on and thinking back to when I started building WordPress plugins, I could’ve saved a lot of time and avoided a lot of anxiety if I’d known where to look.

1. Developer Workshop:
 
 What I Wish I’d Known When I Started Erick Hitter @ethitter https://ethitter.com/
2. PREAMBLE Please, interrupt
 and ask questions
3. INTRO Why should
 developers care?
4. Why does this matter? • Helps future-proof your code • Makes your code easier to maintain • Easier for others to learn and maintain your code • Reduces duplication
5. Why does this matter? • Security • Performance • Scalability
6. FIRST Can’t check if the user’s logged in until init
7. Why? • WordPress checks the user login between the after_setup_theme and init actions
8. So? • WordPress may protect you, and it may work earlier, but it can’t be relied on • Can’t load code at the plugins_loaded action based on the user • Theme setup can’t take user into account
9. SECOND Query results aren’t available until wp
10. Practical implications • Most conditionals aren’t available before wp • Can’t use query conditionals at init or in any earlier hooks • Can conditionally load code in the admin, or not, but that’s about it
11. THIRD Never build a manual link again
12. Link Functions •get_permalink() •get_page_by_path( 'about' ) •get_post_type_archive_link( 'waffles' ) •user_trailingslashit() •get_year_link() •get_adjacent_post()
13. Link Functions •add_query_arg() •remove_query_arg()
14. Link Functions •set_url_scheme()
 
 
 
 Force HTTP URLs to HTTPS, vice versa, and more
15. Link Functions •home_url( '/' )
 
 
 
 Many more in
 wp-includes/link-template.php.
16. The importance of slashes • WP’s permalink structure controls if URLs should end in a slash or not. • WP redirects requests to the “incorrect” form of the permalink. • Therefore, use user_trailingslashit() to avoid unnecessary redirects.
17. FOURTH Escaping and Sanitization
18. Why? • Security!!! User input is untrustworthy. • WordPress makes this really easy • Escaping functions for handling output • Sanitization functions for cleaning data to save
19. Escaping Functions •esc_attr() •esc_html() •esc_url() •esc_textarea()
20. Sanitization Functions •sanitize_text_field() •sanitize_email() •sanitize_user()
21. An Exception • Normally, almost all output should be escaped • WordPress template tags are a rare exception • Otherwise, always assume nefarious intent, even by “trusted” users such as administrators
22. An Exception • There’s really no excuse for not sanitizing user input
23. http://xkcd.com/327/
24. FIFTH Nonces
25. Remember how we
 don’t trust the user? • Intent is just as important as input sanitization • Should the user have been able to do that thing, in the way they did so?
26. Examples • Did the user really click the “delete” button? • Did this request originate from where we expected?
27. nonce Functions •wp_create_nonce() •wp_verify_nonce() •wp_nonce_field()
28. Caveats • User ID is part of their creation, so can’t be used for logged-out requests • Actually valid for a time period, not number of uses • Regardless, they play an important part in protecting against CSRF
29. SIXTH Ajax is easy with WordPress
30. Ajax • Hook your function to one of two variable actions • Use the same action name with the request to admin-ajax.php •check_ajax_referer() or use a nonce
31. Ajax •wp_ajax_{$your_action} •wp_ajax_nopriv_{$your_action} • Hook to both if logged-in state isn’t relevant.
32. SEVENTH REST API
 Framework
33. Why? • Framework introduced in WordPress 4.4 • Doesn’t run in admin context, unlike admin-ajax • Much simpler than creating custom REST endpoints • Obeys Core’s permalinks, making requests cacheable
34. How? •register_rest_route( $namespace, $route, $args )
35. EIGHTH Database Interactions
36. Database Interactions • Use custom post types and custom taxonomies instead. • If you must, always $wpdb->prepare() your queries.
37. Database Interactions •$wpdb->get_var() •$wpdb->get_col() •$wpdb->get_row() •$wpdb->insert( $table, $data, $format ) •$wpdb->update( $table, $data, $where, $format, $where_format ) •$wpdb->query()
38. NINTH Enqueue All The Things
39. Register, then enqueue! •wp_register_style() •wp_register_script()
40. Enqueue! •wp_enqueue_style() •wp_enqueue_script()
41. But why? • Reusable • Dependencies • Versioning • Minification • Concatenation • CDN
42. TENTH Cache All The Things
43. Caching • Transients • Object Cache
44. ELEVENTH Remote Requests
45. WP HTTP API •wp_remote_get() •wp_remote_post() •wp_remote_head() •wp_remote_request() •wp_remote_retrieve_response_code()
46. TWELFTH Roles & Capabilities
47. Roles • Don’t check a user’s role, rather check if that user has a specific capability • Roles can change at runtime • Native capabilities can be taken away from roles • Specific user’s capabilities can be filtered • Familiar with user levels? Ignore them too.
48. Capabilities • Add to specific user roles whose members need those abilities • Control access by checking a user’s capabilities • Can add same capability to multiple roles • Can also remove a capability from all roles, blocking all access
49. Capabilities • Don’t add custom capabilities unless they’re necessary • Often, a native capability that WordPress uses for related functionality can be leveraged instead
50. Functions • current_user_can() • user_can() • add_role() • WP_Role::add_cap()
51. THIRTEENTH Rewrites
52. Rewrite Rules • aka “Pretty Permalinks” • They don’t use query strings, improving cacheability • Simplifies routing and parsing a user request • Provides access to request variables through WP_Query and other Core APIs
53. Rewrite Rules • Consider replacing custom rewrite rules with REST API endpoints, when feasible
54. FOURTEENTH Miscellany
55. Miscellany •get_queried_object() •get_queried_object_id() •validate_file()
56. Miscellany •wp_parse_args() •wp_list_pluck()
57. Thanks Erick Hitter @ethitter https://ethitter.com/ https://ethitter.com/p/9425/