Just like weekday, WordPress uses month global variable to store the month names. It is a single dimensional array set in [wordpress root folder/wp-includes/locale.php]. It stores the localized values of the month names.

Plugin and theme developers can access this global variable, however, to retrieve time and date information about posts within a loop the functions mentioned in weekday can be used.

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WordPress stores in the abbreviations of weekday names in weekday_abbrev weekday variable. It is a single dimensional array, indexed by the weekday name and is set in [wordpress root folder]/wp-includes/locale.php. Just like weekday global variable, weekday_abbrev stores localized values.

Plugin and theme developers can use weekday_abbrev to get abbreviation of a specified weekday name.

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WordPress uses weekday global variable to access, exactly what it says, names of the weekdays. It is a one dimensional array set in the file [wordpress root folder]/wp-includes/locale.php. It stores localized values. Additional global variables like weekday_initial, weekday_abbrev, month, month_abbrev are also defined.

WordPress uses weekday internally. WordPress provides following functions, defined in [wordpress root folder]/wp-includes/template-general-functions.php for use within the loop:

• the_date($format=’ ‘, $before=’ ‘, $after=’ ‘, $echo = true): access date details of the current post.
• the_time($format=’ ‘): access time details of the current post.

The weekday can be accessed by using the format options specified here

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monthnum is a WordPress query string variable that stores the two digit month number. It can be used to retrieve archive of posts posted in a certain month, even across years. When a particular post is being displayed, it contains the month when the post was published.

WordPress uses this global variable internally when the archives are requested. Plugin and theme developers can use monthnum to access the month requested or for the month of the current post. Day f the current post can be accessed using day.

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day is a WordPress query string variable that can used to request archive of posts published on a certain day, across months and years. day global variable stores day of the current post. It is set in the function setup_postdata($post) defined in [wordpress root folder]/wp-includes/functions.php.

WordPress uses this global variable internally, e.g., to form the HTML title when any archive is requested. Plugin and theme developers can use day to get day of the current post.

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Technorati tags: day, current post.

The global variable posts stores the results of a WordPress query as a single dimensional array. It is set in the method register_globals() of class WP.

Plugin and theme developers can use this global variable to access results of the query outside the loop.

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A WordPress post can be forced to have a teaser by inserting the HTML markup <!-- more --> after the desired teaser in the post. WordPress then splits this into the teaser and the main content. When an explicit excerpt for a post is not specified, this teaser is used as an excerpt. more global variable is used to indicate whether the entire page of the post is to be displayed or only the teaser. Teasers can be included in every page of the post. It is set in the function setup_postdata($post) defined in [wordpress root folder]/wp-includes/functions.php.

WordPress uses more global variable internally to determine whether only the teaser has to be displayed or the entire page of the post. Whether the teaser has to be displayed when the entire page of the post is displayed or not can also be specified by including the HTML markup <!-- noteaser --> in the post. Plugin and theme developers can use this global variable if a different behavior is desired.

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WordPress sets is_winIE and is_macIE global variables to identify Microsoft Internet Explorer as part of browser detection in [wordpress root folder]/wp-includes/vars.php. They are set by looking for strings MSIE and Win or Mac in the HTTP_USER_AGENT server variable. It also sets another variable is_IE which is set to true if the browser is Microsoft Internet Explorer on Microsoft Windows or Macs.

Along with these, it also sets the variables is_lynx, is_gecko, is_opera and is_NS4 to identify Lynx, Gecko based browsers, Opera and Netscape 4.0 respectively.

Plugin and theme authors can use these global variables to identify browsers to handle any browser specific features.

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max_num_pages represents the number of pages when any WordPress archive is displayed. It is set using the posts_per_page global variable. It is calculated and set in the functions next_posts_link($label=’Next Page »’, $max_page = 0) and posts_nav_link($sep=’ — ‘, $prelabel=’« Previous Page’, $nxtlabel=’Next Page »’) defined in [wordpress root folder]/wp-includes/template-functions-links.php.

WordPress uses this global variable internally to create the next and previous links for navigation in an archive. Plugin and theme authors need not access this global variable directly.

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WordPress allows configuration for setting the number of posts to be displayed whenever an index archive (the typical homepage) or other archives like category or monthly archives are displayed. This option can be configured in the Blog Pages field Reading tab under Options menu in the administration User Interface. Note that there is a separate field for configuration number of posts to be displayed for syndication (feeds).

posts_per_page is set in the method get_posts of WP_Query.

Plugin and theme authors need not access this global variable directly. WordPress uses it internally to calculate the number of posts to be displayed.

Since the same setting is used for all archives Matt Read has developed a plugin where posts per page setting can be set for different types of archives, e.g., search, category, home, monthly, yearly, etc.

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Technorati tags: posts_per_page, archives

m is a WordPress query string variable which can be used to request posts posted at a certain time. It is parsed in the method get_posts() of wp_query.

m allows specifying the time upto the second. Its format is yyyymmddhhmmss, where

• yyyy: year
• mm: month number
• dd: day of the week
• hh: hour
• mm: minute
• ss: second

In short, m can be used to query posts with a specific timestamp. As an example, http://iface.wordpress.com/?m=200607031745 returns the posts posted on 3rd July 2005 @ 17:45. Of course all the fields are not compulsory, you can request the posts posted in July 2005 by using http://iface.wordpress.com/?m=200607.

There is some redundancy as other query string variables like year, monthnum, day, hour, minute and second can be achieved to the same effect.

The plugin developers need not access this global variable since this is purely a query string variable.

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WordPress supports Localization using the gettext framework. l10n global variable is used to store all the readers corresponding to the different languages supported. It is set in the function load_textdomain($domain, $mofile) defined in [wordpress root folder]/wp-includes/wp-l10n.php. Following functions are defined which internally use this function:

• load_default_textdomain(): loads the default textdomain
• load_plugin_textdomain($domain, $path = 'wp-content/plugins'): loads text domain defined in the plugins
• load_theme_textdomain($domain): loads text domain defined in the theme

Loading of the text domain involves looking up for corresponding mo file with the same name as the locale.

The default domain is loaded using the function load_default_textdomain() in [wordpress root folder]/wp-settings.php.

Plugin or theme developers need not use this global variable directly. WordPress provides functions to translate text in localized language.

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Technorati tags: localization, internationalization, l10n, i18n, gettext

WordPress supports internationalization (i18n) and localization (l10n). A locale is indicated by the combination of the language and the region (usually the country). It is represented with ISO codes of the language and countries, e.g., en_US for US Enligsh, en_GB for British English and so on. US English is the default locale. locale global variable is used to store the current locale. It is set in the function get_locale() defined in [wordpress root folder]/wp-includes/wp-l10n.php.

WordPress uses this global variable internally to load the current locale. If the locale is not set already, it takes the value of WPLANG defined in [wordpress root folder]/wp-config.php. If that is empty it falls back to the default locale which is US English.

Plugin and theme developers need not use this global variable as it is part of the internationalization and localization framework. WordPress provides functions for translation.

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Technorati tags: localization, internationalization, i18n, l10n, locale

Like is_apache, is_IIS is part of the web server detection. It is set in [wordpress root folder]/wp-includes/vars.php in the following manner:

$is_IIS=strstr($_SERVER['SERVER_SOFTWARE'], 'Microsoft-IIS')
           ? 1 : 0;

As mentioned in is_apache, the server variable SERVER_SOFTWARE can be blocked by certain hosts. It can be forcibly set to 1 if WordPress is running on Microsoft IIS.

A classic example of using the server detection is the pluggable function wp_redirect function, which handles the difference between IIS and Apache redirects. Plugin and theme developers should similarly use it for web server specific features.

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is_apache global variable can be used to detect which webserver WordPress is running on. It is set in [wordpress root folder]/wp-includes/vars.php as part of the server detection code. It is set in the following manner:

$is_apache=(strstr($_SERVER['SERVER_SOFTWARE'], 'Apache') ||
     strstr($_SERVER['SERVER_SOFTWARE'], 'LiteSpeed')) ? 1 : 0;

is_apache is set to 1 (which means true) if the webserver is either Apache or Litespeed (WordPress.com, i.e., even this blog runs on Litespeed today), which means that both of them can be considered to be practically the same. The other webserver that WordPress supports is Microsoft IIS which is indicated using the global variable is_IIS.

It is possible that certain hosts block the server variable SERVER_SOFTWARE, which can cause problems in using permalinks. is_apache global variable can be forcibly set to 1 for an assured Apache/Litespeed webserver as advised here.

Plugin and theme developers can use these global variables for any web server specific features. One of the biggest features of WordPress – permalinks – requires identification of the web server.

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post_meta_cache is one more global variable used for caching as WordPress. It is a multi-dimensional array which stores the custom fields for a post. The custom fields are stored by the post ID and then by the custom field key. Multiple instances of custom fields are allowed.

Plugin and theme developers need not access post_meta_cache directly, it is used by WordPress internally in the following internal and template functions.

Internal Functions

• add_post_meta($post_id, $key, $value, $unique = false): adds custom field with specified key and value to the specified post. If unique is true, another custom field with duplicate key is not added. This can be used by developers who are developing plugins for the the admin area, especially for adding more information to the post structure.
• delete_post_meta($post_id, $key, $value): deletes the custom field with specified key and value from the specified post.
• get_post_meta($post_id, $key, $single = false): returns custom field value for specified key for the specified post.
• update_post_meta($post_id, $key, $value, $prev_value = ''): updates the custom field value for specified key in the specified post.

Template Functions

• get_post_custom($post_id = 0): returns all the custom fields for specified post as an array. If post ID is not specified, current post is considered.
• get_post_custom_keys(): returns keys of all the custom fields for specified post as an array
• get_post_custom_values($key = ''): returns all values of the specified custom fields key for specified post as an array
• post_custom($key = ''): returns all the custom fields with specified key for the current post.
• the_meta(): displays all the custom fields of the current post as a unordered list.

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Technorati tags: post_meta_cache, custom fields, post meta

WordPress provides a facility of hooks. They can be used by plugin and theme developers can modify custom behavior at different points in WordPress. Mark Jaquith has compiled a directory of hooks provided by WordPress.

Actions and filters are two different types of hooks, they are semnatically different but syntactically the same. These filters and actions are stored in the wp_filter global variable. It is set using add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) function defined in [wordpress root folder]/wp-includes/functions.php.

WordPress adds certain default actions and filters, most of which are done in [wordpress root folder]/wp-includes/default-filters.php. Function do_action($tag, $arg = ”) is used internally by WordPress to invoke the different registered filters and actions.

Plugin and theme developers can define custom functions and add them as filters or actions using the following functions provided by WordPress:

• add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1): to register filters
• add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1): to register actions
• remove_filter($tag, $function_to_remove, $priority = 10, $accepted_args = 1): to remove filters
• remove_action($tag, $function_to_remove, $priority = 10, $accepted_args = 1): to remove actions

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Technorati tags: wp_filter, hooks, actions, filters, add_action, add_filter, remove_action, remove_filter, do_action

WordPress stores version of the MySQL database currently being used in the wp_db_version global variable. Like wp_version, it is set in [wordpress root folder]/wp-includes/version.php.

Plugin and theme developers can use this variable to check for their features specific to a database version.

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This global variable indicates whether the current user wants to use rich editing interface (by default using TinyMCE) for creating/editing posts and comments. Since WordPress 2.0, the option of rich editing is set per user, which can be accessed by using the checkbox, “Use the visual rich editor when writing”, in Admin Panel->Users->Your Profile.

richedit is set in the functions get_post_to_edit($id) and get_comment_to_edit($id) in the [wordpress-root-folder]/wp-admin/admin-functions.php. It is set using the function get_user_option('rich_editing').

WordPress defines an additional function user_can_richedit which, in addition to checking this option, checks whether the browser supports rich editing or not. Plugin developers can use this function, when using the global variable directly it should not noted that unlike lot of others, this global variable is defined as part of the admin functions.

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Technorati tags: richedit, user options, rich_editing, wysiwyg editor.

WordPress uses page_cache global variable to cache static pages by their ID. Caching can notably improve performance by retrieving data from memory and avoiding repeated queries to the database. It is an array set in the function update_page_cache(&$pages) defined in [wordpress root folder]/wp-includes/functions.php.

WordPress uses page_cache internally in the functions to retrieve pages:

• get_pages($args = ''): retrieves the static pages according to the arguments provided. Following arguments are supported:
  • child_of: if specified, the function retrieves the children of specified page ID.
  • sort_column: attribute of the page that should be used for sorting, which is implemented as column name in the wp_posts table in the database.
  • sort_order: order for sorting, currently supports ASC and DESC.
  • exclude: includes IDs of pages that should be excluded from the retrieval.
• get_page_children($page_id, $pages): retrieves child pages of the specified page. If $pages argument is empty, $page_cache global variable is used.

Plugin and theme developers can use page_cache to write custom functions which involve retrieving page data.

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WordPress uses numpages global variable to store the number of pages in a multipage post. It is set in the function setup_postdata($post) defined in [wordpress root folder]/wp-includes/functions.php. The split pages are stored in the global variable pages.

Theme developers can use numpages global variable to display the count of split pages in a multipage post.

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Technorati tags: pages, multipage

Just like category_cache, WordPress uses post_cache global variable to cache all the posts by their IDs. It is set in the function update_post_caches($posts) defined in [wordpress root folder]/wp-includes/functions.php. post_cache is an array and indexes post by the post ID. WordPress provides function clean_post_cache($id) to cleanup or unset the post for the specified ID.

post_cache is internally used by WordPress in following functions:

• get_posts($args): codex document
• get_children($post = 0, $output = OBJECT): returns child posts of the specified post. If not post is specified, children of current post are returned. This is specifically useful when retrieving heirarchical static pages.

Plugin and theme developers can use the cache when retrieving the entire posts or individual fields. They can also use update_post_caches($posts) to update the cache. This function also updates the category cache using update_post_category_cache($post_ids).

Technorati tags: post_cache, cache, post.

WordPress uses category_cache global variable to cache categories by posts. This means that it can be queried for categories by providing the post ID. It is a two-dimensional array set in the function update_post_category_cache($post_ids) defined in [wordpress root folder]/wp-includes/functions.php.

The cache can improve performance by saving repeated trips to the database for querying the same data.

WordPress uses category_cache internally in the following functions:

• get_the_category($post_id = false): returns categories the specified post is classified under. An array of the categories is returned.
• in_category($category): tells whether the current post is in the specified category or not.

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Technorati tags: category_cache

WordPress uses this global variable to store the current PHP file being executed, e.g., post.php or edit.php. It is set in [wordpress root folder]/wp-includes/vars.php, which is included in [wordpress root folder/wp-includes/settings.php.

pagenow is used to identify the current action being executed. Ideally, plugin and theme developers need not use this global variable, it is used internally by WordPress. Conditional Tags should be used to identify the current template file.

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Technorati tags: pagenow, current action

This global variable stores the requested page number of a multipage post that has to be shown. It is set in the function setup_postdata($post) defined in [wordpress root folder]/wp-includes/functions.php. The variable page in the WordPress request (query string) is used to set this global variable. The multipage content of the post is stored in the global variable pages.

page does not indicate the page number of a paginated archive, it is used only for a multipage post.

Plugin and theme developers can use this variable to identify the requested page number of the current post being displayed.

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Technorati tags: page, current page, pages, multipage