WordPress Codex is a Useful Reference
In the WordPress Codex, you will find list of Conditional Tags, and Function References
WP_Query is a big one. The Template Hierarchy has a great chart for how to name your theme files for custom themeing.
Before taking user input and displaying out on page or storing in database, call the appropriate one of these Data Validation functions. If you don’t, there is a security risk.
When learning wordpress, here are some useful functions to look up…
the_title()
the_content()
the_permalink()
the_author()
the_author_meta()
the_time()
the_modified_time()
the_date()
the_excerpt()
the_meta()
the_category()
the_tags()
get_the_category()
get_the_time()
get_post_custom()
get_template_part() – includes a template PHP file of any name.
is_home()
is_front_page()
is_page()
is_admin()
is_single()
post_nav_link()
previous_posts_link()
next_posts_link()
rewind_posts() — reset loop in order to do a second loop
query_posts() — call before loop for minor tweaks passed into its parameter
get_posts() — for when more customization of loop is needed.
setup_postdata($post) — need to use “global $post;” and call the param “$post”
wp_reset_postdata()
get_current_screen() — useful for debugging
wp_list_pages() — displays a list of WordPress pages as links.