Title: wp-includes/functions.php | Page 6 of 10 | Developer.WordPress.org --- # File: wp-includes/functions.php * function[wp_find_hierarchy_loop_tortoise_hare()](https://developer.wordpress.org/reference/functions/wp_find_hierarchy_loop_tortoise_hare/) * Uses the “The Tortoise and the Hare” algorithm to detect loops. * Used by [1 function](https://developer.wordpress.org/reference/functions/wp_find_hierarchy_loop_tortoise_hare/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/wp_find_hierarchy_loop_tortoise_hare/#uses) | Source: [wp-includes/functions.php:7242](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7242-L7272) * function[send_frame_options_header()](https://developer.wordpress.org/reference/functions/send_frame_options_header/) * Sends a HTTP header to limit rendering of pages to same origin iframes. * Used by [0 functions](https://developer.wordpress.org/reference/functions/send_frame_options_header/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/send_frame_options_header/#uses) | Source: [wp-includes/functions.php:7282](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7282-L7287) * function[wp_allowed_protocols()](https://developer.wordpress.org/reference/functions/wp_allowed_protocols/) * Retrieves a list of protocols to allow in HTML attributes. * Used by [11 functions](https://developer.wordpress.org/reference/functions/wp_allowed_protocols/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/wp_allowed_protocols/#uses) | Source: [wp-includes/functions.php:7331](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7331-L7350) * function[wp_timezone_choice()](https://developer.wordpress.org/reference/functions/wp_timezone_choice/) * Gives a nicely-formatted list of timezone strings. * Used by [0 functions](https://developer.wordpress.org/reference/functions/wp_timezone_choice/#used-by) | Uses [8 functions](https://developer.wordpress.org/reference/functions/wp_timezone_choice/#uses) | Source: [wp-includes/functions.php:6759](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6759-L6947) * function[_cleanup_header_comment()](https://developer.wordpress.org/reference/functions/_cleanup_header_comment/) * Strips close comment and close php tags from file headers used by WP. * Used by [2 functions](https://developer.wordpress.org/reference/functions/_cleanup_header_comment/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/_cleanup_header_comment/#uses) | Source: [wp-includes/functions.php:6960](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6960-L6962) * function[wp_scheduled_delete()](https://developer.wordpress.org/reference/functions/wp_scheduled_delete/) * Permanently deletes comments or posts of any type that have held a status of ‘ trash’ for the number of days defined in EMPTY_TRASH_DAYS. * Used by [0 functions](https://developer.wordpress.org/reference/functions/wp_scheduled_delete/#used-by) | Uses [8 functions](https://developer.wordpress.org/reference/functions/wp_scheduled_delete/#uses) | Source: [wp-includes/functions.php:6974](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6974-L7014) * function[get_file_data()](https://developer.wordpress.org/reference/functions/get_file_data/) * Retrieves metadata from a file. * Used by [6 functions](https://developer.wordpress.org/reference/functions/get_file_data/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/get_file_data/#uses) | Source: [wp-includes/functions.php:7036](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7036-L7074) * hook[extra_{$context}_headers](https://developer.wordpress.org/reference/hooks/extra_context_headers/) * Filters extra file headers by context. * Used by [1 function](https://developer.wordpress.org/reference/hooks/extra_context_headers/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/extra_context_headers/#uses) | Source: [wp-includes/functions.php:7057](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7057-L7057) * function[__return_true()](https://developer.wordpress.org/reference/functions/__return_true/) * Returns true. * Used by [0 functions](https://developer.wordpress.org/reference/functions/__return_true/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/__return_true/#uses) | Source: [wp-includes/functions.php:7087](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7087-L7089) * function[__return_false()](https://developer.wordpress.org/reference/functions/__return_false/) * Returns false. * Used by [0 functions](https://developer.wordpress.org/reference/functions/__return_false/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/__return_false/#uses) | Source: [wp-includes/functions.php:7102](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7102-L7104) * function[force_ssl_admin()](https://developer.wordpress.org/reference/functions/force_ssl_admin/) * Determines whether to force SSL used for the Administration Screens. * Used by [5 functions](https://developer.wordpress.org/reference/functions/force_ssl_admin/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/force_ssl_admin/#uses) | Source: [wp-includes/functions.php:6418](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6418-L6428) * function[__return_zero()](https://developer.wordpress.org/reference/functions/__return_zero/) * Returns 0. * Used by [0 functions](https://developer.wordpress.org/reference/functions/__return_zero/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/__return_zero/#uses) | Source: [wp-includes/functions.php:7115](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L7115-L7117) * function[wp_guess_url()](https://developer.wordpress.org/reference/functions/wp_guess_url/) * Guesses the URL for the site. * Used by [5 functions](https://developer.wordpress.org/reference/functions/wp_guess_url/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/wp_guess_url/#uses) | Source: [wp-includes/functions.php:6440](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6440-L6477) * function[wp_suspend_cache_addition()](https://developer.wordpress.org/reference/functions/wp_suspend_cache_addition/) * Temporarily suspends cache additions. * Used by [3 functions](https://developer.wordpress.org/reference/functions/wp_suspend_cache_addition/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/wp_suspend_cache_addition/#uses) | Source: [wp-includes/functions.php:6495](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6495-L6503) * function[wp_suspend_cache_invalidation()](https://developer.wordpress.org/reference/functions/wp_suspend_cache_invalidation/) * Suspends cache invalidation. * Used by [0 functions](https://developer.wordpress.org/reference/functions/wp_suspend_cache_invalidation/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/wp_suspend_cache_invalidation/#uses) | Source: [wp-includes/functions.php:6519](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6519-L6525) * function[is_main_site()](https://developer.wordpress.org/reference/functions/is_main_site/) * Determines whether a site is the main site of the current network. * Used by [18 functions](https://developer.wordpress.org/reference/functions/is_main_site/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_main_site/#uses) | Source: [wp-includes/functions.php:6539](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6539-L6551) * function[is_main_network()](https://developer.wordpress.org/reference/functions/is_main_network/) * Determines whether a network is the main network of the Multisite installation. * Used by [4 functions](https://developer.wordpress.org/reference/functions/is_main_network/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_main_network/#uses) | Source: [wp-includes/functions.php:6583](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6583-L6595) * hook[global_terms_enabled](https://developer.wordpress.org/reference/hooks/global_terms_enabled/) * Filters whether global terms are enabled. * Used by [0 functions](https://developer.wordpress.org/reference/hooks/global_terms_enabled/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/global_terms_enabled/#uses) | Source: [wp-includes/functions.php:6239](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6239-L6239) * function[wp_timezone_override_offset()](https://developer.wordpress.org/reference/functions/wp_timezone_override_offset/) * Modifies gmt_offset for smart timezone handling. * Used by [0 functions](https://developer.wordpress.org/reference/functions/wp_timezone_override_offset/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/wp_timezone_override_offset/#uses) | Source: [wp-includes/functions.php:6677](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6677-L6690) * function[_wp_timezone_choice_usort_callback()](https://developer.wordpress.org/reference/functions/_wp_timezone_choice_usort_callback/) * Sort-helper for timezones. * Used by [0 functions](https://developer.wordpress.org/reference/functions/_wp_timezone_choice_usort_callback/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/_wp_timezone_choice_usort_callback/#uses) | Source: [wp-includes/functions.php:6702](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6702-L6747) * hook[doing_it_wrong_run](https://developer.wordpress.org/reference/hooks/doing_it_wrong_run/) * Fires when the given function is being used incorrectly. * Used by [1 function](https://developer.wordpress.org/reference/hooks/doing_it_wrong_run/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/doing_it_wrong_run/#uses) | Source: [wp-includes/functions.php:6123](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6123-L6123) * hook[doing_it_wrong_trigger_error](https://developer.wordpress.org/reference/hooks/doing_it_wrong_trigger_error/) * Filters whether to trigger an error for _doing_it_wrong() calls. * Used by [1 function](https://developer.wordpress.org/reference/hooks/doing_it_wrong_trigger_error/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/doing_it_wrong_trigger_error/#uses) | Source: [wp-includes/functions.php:6136](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6136-L6136) * function[is_lighttpd_before_150()](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/) * Determines whether the server is running an earlier than 1.5.0 version of lighttpd. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/#uses) | Source: [wp-includes/functions.php:6270](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6270-L6275) * function[apache_mod_loaded()](https://developer.wordpress.org/reference/functions/apache_mod_loaded/) * Determines whether the specified module exist in the Apache config. * Used by [2 functions](https://developer.wordpress.org/reference/functions/apache_mod_loaded/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/apache_mod_loaded/#uses) | Source: [wp-includes/functions.php:6288](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6288-L6319) * function[iis7_supports_permalinks()](https://developer.wordpress.org/reference/functions/iis7_supports_permalinks/) * Checks if IIS 7+ supports pretty permalinks. * Used by [4 functions](https://developer.wordpress.org/reference/functions/iis7_supports_permalinks/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/iis7_supports_permalinks/#uses) | Source: [wp-includes/functions.php:6330](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6330-L6355) * hook[iis7_supports_permalinks](https://developer.wordpress.org/reference/hooks/iis7_supports_permalinks/) * Filters whether IIS 7+ supports pretty permalinks. * Used by [1 function](https://developer.wordpress.org/reference/hooks/iis7_supports_permalinks/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/iis7_supports_permalinks/#uses) | Source: [wp-includes/functions.php:6354](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6354-L6354) * function[_deprecated_function()](https://developer.wordpress.org/reference/functions/_deprecated_function/) * Marks a function as deprecated and inform when it has been used. * Used by [425 functions](https://developer.wordpress.org/reference/functions/_deprecated_function/#used-by) | Uses [4 functions](https://developer.wordpress.org/reference/functions/_deprecated_function/#uses) | Source: [wp-includes/functions.php:5643](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L5643-L5700) * function[validate_file()](https://developer.wordpress.org/reference/functions/validate_file/) * Validates a file name and path against an allowed set of rules. * Used by [14 functions](https://developer.wordpress.org/reference/functions/validate_file/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/validate_file/#uses) | Source: [wp-includes/functions.php:6372](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L6372-L6408) * hook[deprecated_function_run](https://developer.wordpress.org/reference/hooks/deprecated_function_run/) * Fires when a deprecated function is called. * Used by [1 function](https://developer.wordpress.org/reference/hooks/deprecated_function_run/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/deprecated_function_run/#uses) | Source: [wp-includes/functions.php:5654](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L5654-L5654) * hook[deprecated_function_trigger_error](https://developer.wordpress.org/reference/hooks/deprecated_function_trigger_error/) * Filters whether to trigger an error for deprecated functions. * Used by [1 function](https://developer.wordpress.org/reference/hooks/deprecated_function_trigger_error/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/hooks/deprecated_function_trigger_error/#uses) | Source: [wp-includes/functions.php:5663](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/functions.php#L5663-L5663) [Previous Page](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/5/?output_format=md) [1](https://developer.wordpress.org/reference/files/wp-includes/functions.php/?output_format=md)… [4](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/4/?output_format=md) [5](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/5/?output_format=md) 6 [7](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/7/?output_format=md) [8](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/8/?output_format=md)… [10](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/10/?output_format=md) [Next Page](https://developer.wordpress.org/reference/files/wp-includes/functions.php/page/7/?output_format=md)