Title: Functions | Page 36 of 49 | Developer.WordPress.org --- # Functions * function[install_themes_upload()](https://developer.wordpress.org/reference/functions/install_themes_upload/) * Displays a form to upload themes from zip files. * Used by [0 functions](https://developer.wordpress.org/reference/functions/install_themes_upload/#used-by) | Uses [6 functions](https://developer.wordpress.org/reference/functions/install_themes_upload/#uses) | Source: [wp-admin/includes/theme-install.php:195](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-admin/includes/theme-install.php#L195-L210) * function[install_theme_information()](https://developer.wordpress.org/reference/functions/install_theme_information/) * Displays theme information in dialog box form. * Used by [0 functions](https://developer.wordpress.org/reference/functions/install_theme_information/#used-by) | Uses [8 functions](https://developer.wordpress.org/reference/functions/install_theme_information/#uses) | Source: [wp-admin/includes/theme-install.php:255](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-admin/includes/theme-install.php#L255-L271) * function[install_theme_search_form()](https://developer.wordpress.org/reference/functions/install_theme_search_form/) * Displays search form for searching themes. * Used by [1 function](https://developer.wordpress.org/reference/functions/install_theme_search_form/#used-by) | Uses [7 functions](https://developer.wordpress.org/reference/functions/install_theme_search_form/#uses) | Source: [wp-admin/includes/theme-install.php:91](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-admin/includes/theme-install.php#L91-L142) * function[in_category()](https://developer.wordpress.org/reference/functions/in_category/) * Checks if the current post is within any of the given categories. * Used by [0 functions](https://developer.wordpress.org/reference/functions/in_category/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/in_category/#uses) | Source: [wp-includes/category-template.php:257](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/category-template.php#L257-L263) * function[in_the_loop()](https://developer.wordpress.org/reference/functions/in_the_loop/) * Determines whether the caller is in the Loop. * Used by [3 functions](https://developer.wordpress.org/reference/functions/in_the_loop/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/in_the_loop/#uses) | Source: [wp-includes/query.php:964](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L964-L972) * function[iso8601_timezone_to_offset()](https://developer.wordpress.org/reference/functions/iso8601_timezone_to_offset/) * Given an ISO 8601 timezone, returns its UTC offset in seconds. * Used by [0 functions](https://developer.wordpress.org/reference/functions/iso8601_timezone_to_offset/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/iso8601_timezone_to_offset/#uses) | Source: [wp-includes/formatting.php:3719](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/formatting.php#L3719-L3730) * function[iso8601_to_datetime()](https://developer.wordpress.org/reference/functions/iso8601_to_datetime/) * Given an ISO 8601 (Ymd\TH:i:sO) date, returns a MySQL DateTime (Y-m-d H:i:s) format used by post_date[_gmt]. * Used by [4 functions](https://developer.wordpress.org/reference/functions/iso8601_to_datetime/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/iso8601_to_datetime/#uses) | Source: [wp-includes/formatting.php:3741](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/formatting.php#L3741-L3759) * function[is_404()](https://developer.wordpress.org/reference/functions/is_404/) * Determines whether the query has resulted in a 404 (returns no results). * Used by [11 functions](https://developer.wordpress.org/reference/functions/is_404/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_404/#uses) | Source: [wp-includes/query.php:858](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L858-L867) * function[is_active_sidebar()](https://developer.wordpress.org/reference/functions/is_active_sidebar/) * Determines whether a sidebar contains widgets. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_active_sidebar/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_active_sidebar/#uses) | Source: [wp-includes/widgets.php:983](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/widgets.php#L983-L998) * function[is_active_widget()](https://developer.wordpress.org/reference/functions/is_active_widget/) * Determines whether a given widget is displayed on the front end. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_active_widget/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_active_widget/#uses) | Source: [wp-includes/widgets.php:914](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/widgets.php#L914-L937) * function[is_admin()](https://developer.wordpress.org/reference/functions/is_admin/) * Determines whether the current request is for an administrative interface page. * Used by [77 functions](https://developer.wordpress.org/reference/functions/is_admin/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_admin/#uses) | Source: [wp-includes/load.php:1356](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/load.php#L1356-L1364) * function[is_admin_bar_showing()](https://developer.wordpress.org/reference/functions/is_admin_bar_showing/) * Determines whether the admin bar should be showing. * Used by [4 functions](https://developer.wordpress.org/reference/functions/is_admin_bar_showing/#used-by) | Uses [6 functions](https://developer.wordpress.org/reference/functions/is_admin_bar_showing/#uses) | Source: [wp-includes/admin-bar.php:1343](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/admin-bar.php#L1343-L1381) * function[is_allowed_http_origin()](https://developer.wordpress.org/reference/functions/is_allowed_http_origin/) * Determines if the HTTP origin is an authorized one. * Used by [1 function](https://developer.wordpress.org/reference/functions/is_allowed_http_origin/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_allowed_http_origin/#uses) | Source: [wp-includes/http.php:484](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/http.php#L484-L504) * function[is_archive()](https://developer.wordpress.org/reference/functions/is_archive/) * Determines whether the query is for an existing archive page. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_archive/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_archive/#uses) | Source: [wp-includes/query.php:161](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L161-L170) * function[is_archived()](https://developer.wordpress.org/reference/functions/is_archived/) * Checks if a particular blog is archived. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_archived/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_archived/#uses) | Source: [wp-includes/ms-blogs.php:732](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/ms-blogs.php#L732-L734) * function[is_attachment()](https://developer.wordpress.org/reference/functions/is_attachment/) * Determines whether the query is for an existing attachment page. * Used by [9 functions](https://developer.wordpress.org/reference/functions/is_attachment/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_attachment/#uses) | Source: [wp-includes/query.php:213](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L213-L222) * function[is_author()](https://developer.wordpress.org/reference/functions/is_author/) * Determines whether the query is for an existing author archive page. * Used by [10 functions](https://developer.wordpress.org/reference/functions/is_author/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_author/#uses) | Source: [wp-includes/query.php:242](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L242-L251) * function[is_avatar_comment_type()](https://developer.wordpress.org/reference/functions/is_avatar_comment_type/) * Check if this comment type allows avatars to be retrieved. * Used by [1 function](https://developer.wordpress.org/reference/functions/is_avatar_comment_type/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_avatar_comment_type/#uses) | Source: [wp-includes/link-template.php:4345](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/link-template.php#L4345-L4358) * function[is_blog_admin()](https://developer.wordpress.org/reference/functions/is_blog_admin/) * Determines whether the current request is for a site’s administrative interface. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_blog_admin/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_blog_admin/#uses) | Source: [wp-includes/load.php:1380](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/load.php#L1380-L1388) * function[is_blog_installed()](https://developer.wordpress.org/reference/functions/is_blog_installed/) * Determines whether WordPress is already installed. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_blog_installed/#used-by) | Uses [11 functions](https://developer.wordpress.org/reference/functions/is_blog_installed/#uses) | Source: [wp-includes/functions.php:1773](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/functions.php#L1773-L1856) * function[is_blog_user()](https://developer.wordpress.org/reference/functions/is_blog_user/) * Checks if the current user belong to a given site. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_blog_user/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_blog_user/#uses) | Source: [wp-includes/deprecated.php:2838](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/deprecated.php#L2838-L2842) * function[is_category()](https://developer.wordpress.org/reference/functions/is_category/) * Determines whether the query is for an existing category archive page. * Used by [12 functions](https://developer.wordpress.org/reference/functions/is_category/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_category/#uses) | Source: [wp-includes/query.php:271](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L271-L280) * function[is_child_theme()](https://developer.wordpress.org/reference/functions/is_child_theme/) * Whether a child theme is in use. * Used by [8 functions](https://developer.wordpress.org/reference/functions/is_child_theme/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_child_theme/#uses) | Source: [wp-includes/theme.php:163](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/theme.php#L163-L167) * function[is_client_error()](https://developer.wordpress.org/reference/functions/is_client_error/) * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_client_error/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_client_error/#uses) | Source: [wp-includes/rss.php:710](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/rss.php#L710-L712) * function[is_comments_popup()](https://developer.wordpress.org/reference/functions/is_comments_popup/) * Determines whether the current URL is within the comments popup window. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_comments_popup/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_comments_popup/#uses) | Source: [wp-includes/deprecated.php:3761](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/deprecated.php#L3761-L3765) * function[is_comment_feed()](https://developer.wordpress.org/reference/functions/is_comment_feed/) * Is the query for a comments feed? * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_comment_feed/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_comment_feed/#uses) | Source: [wp-includes/query.php:433](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L433-L442) * function[is_customize_preview()](https://developer.wordpress.org/reference/functions/is_customize_preview/) * Whether the site is being previewed in the Customizer. * Used by [12 functions](https://developer.wordpress.org/reference/functions/is_customize_preview/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_customize_preview/#uses) | Source: [wp-includes/theme.php:3842](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/theme.php#L3842-L3846) * function[is_date()](https://developer.wordpress.org/reference/functions/is_date/) * Determines whether the query is for an existing date archive. * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_date/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_date/#uses) | Source: [wp-includes/query.php:361](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L361-L370) * function[is_day()](https://developer.wordpress.org/reference/functions/is_day/) * Determines whether the query is for an existing day archive. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_day/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_day/#uses) | Source: [wp-includes/query.php:387](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L387-L396) * function[is_dynamic_sidebar()](https://developer.wordpress.org/reference/functions/is_dynamic_sidebar/) * Determines whether the dynamic sidebar is enabled and used by the theme. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_dynamic_sidebar/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_dynamic_sidebar/#uses) | Source: [wp-includes/widgets.php:953](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/widgets.php#L953-L969) [Previous Page](https://developer.wordpress.org/reference/functions/page/35/?output_format=md) [1](https://developer.wordpress.org/reference/functions/?output_format=md) … [34](https://developer.wordpress.org/reference/functions/page/34/?output_format=md) [35](https://developer.wordpress.org/reference/functions/page/35/?output_format=md) 36 [37](https://developer.wordpress.org/reference/functions/page/37/?output_format=md) [38](https://developer.wordpress.org/reference/functions/page/38/?output_format=md)… [49](https://developer.wordpress.org/reference/functions/page/49/?output_format=md) [Next 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