Source: wp-includes/update.php

Core Update Functions

wp_version_check()

Checks WordPress version against the newest version available on WordPress.org.

wp_version_check( array $extra_stats = array(), bool $force_check = false )

Parameters:

• $extra_stats (array) – Extra statistics to report to the WordPress.org API
• $force_check (bool) – Bypass transient cache and force fresh check. Auto-true if $extra_stats provided.

Returns: void

Behavior:

1. Bails if wp_installing() returns true
2. Respects 1-minute rate limit between checks (unless forced)
3. Collects system info: WP version, PHP, MySQL, locale, extensions, image support
4. POSTs to api.wordpress.org/core/version-check/1.7/
5. Stores result in update_core site transient
6. May trigger wp_maybe_auto_update action if running via cron

Since: 2.3.0

---

wp_update_plugins()

Checks for available plugin updates from WordPress.org.

wp_update_plugins( array $extra_stats = array() )

Parameters:

• $extra_stats (array) – Extra statistics to report to the API

Returns: void

Behavior:

1. Loads wp-admin/includes/plugin.php if needed for get_plugins()
2. Compiles list of all plugins with versions
3. POSTs to api.wordpress.org/plugins/update-check/1.1/
4. Processes third-party updates via Update URI header
5. Stores in update_plugins site transient with structure:
   • response – Plugins with updates available
   • no_update – Plugins at latest version
   • checked – All plugins and their versions
   • translations – Available translation updates

Since: 2.3.0

---

wp_update_themes()

Checks for available theme updates from WordPress.org.

wp_update_themes( array $extra_stats = array() )

Parameters:

• $extra_stats (array) – Extra statistics to report to the API

Returns: void

Behavior:

1. Collects all themes via wp_get_themes()
2. POSTs to api.wordpress.org/themes/update-check/1.1/
3. Processes third-party updates via Update URI header
4. Stores in update_themes site transient

Since: 2.7.0

---

Auto-Update Functions

wp_maybe_auto_update()

Performs WordPress automatic background updates for core, plugins, and themes.

wp_maybe_auto_update()

Returns: void

Behavior:

1. Requires wp-admin/includes/admin.php and class-wp-upgrader.php
2. Instantiates WP_Automatic_Updater
3. Calls $upgrader->run()

Since: 3.7.0

---

Translation Functions

wp_get_translation_updates()

Retrieves all available translation updates across core, plugins, and themes.

wp_get_translation_updates(): object[]

Returns: Array of translation objects with available updates

Behavior:

• Reads update_core, update_plugins, update_themes transients
• Extracts translations array from each
• Returns combined list of translation update objects

Since: 3.7.0

---

UI Helper Functions

wp_get_update_data()

Collects counts and UI strings for available updates (used in admin menu badges).

wp_get_update_data(): array

Returns:

array(
    'counts' => array(
        'plugins'      => int,
        'themes'       => int,
        'wordpress'    => int,  // 0 or 1
        'translations' => int,  // 0 or 1
        'total'        => int,
    ),
    'title' => string,  // e.g., "5 Plugin Updates, 2 Theme Updates"
)

Behavior:

• Respects user capabilities (update_plugins, update_themes, update_core)
• Only counts non-dismissed core updates
• Generates human-readable title string

Since: 3.3.0

---

Internal/Private Functions

_maybe_update_core()

Conditionally triggers core version check if stale (>12 hours).

_maybe_update_core()

Hooked to: admin_init

Since: 2.8.0

---

_maybe_update_plugins()

Conditionally triggers plugin version check if stale (>12 hours).

_maybe_update_plugins()

Hooked to: admin_init

Since: 2.7.0
Access: Private

---

_maybe_update_themes()

Conditionally triggers theme version check if stale (>12 hours).

_maybe_update_themes()

Hooked to: admin_init

Since: 2.7.0
Access: Private

---

Scheduling Functions

wp_schedule_update_checks()

Schedules twice-daily cron events for update checks.

wp_schedule_update_checks()

Behavior:

• Schedules wp_version_check event
• Schedules wp_update_plugins event
• Schedules wp_update_themes event
• All use twicedaily recurrence

Hooked to: init

Since: 3.1.0

---

Cache Functions

wp_clean_update_cache()

Clears all update transient caches.

wp_clean_update_cache()

Behavior:

• Calls wp_clean_plugins_cache() if available, else deletes update_plugins transient
• Calls wp_clean_themes_cache()
• Deletes update_core transient

Hooked to: update_option_WPLANG

Since: 4.1.0

---

Backup Cleanup Functions

wp_delete_all_temp_backups()

Schedules removal of temporary backup directory contents.

wp_delete_all_temp_backups()

Behavior:

• Checks for update locks (core_updater.lock, auto_updater.lock)
• If locked or doing Ajax, reschedules for 1 hour later
• Otherwise hooks _wp_delete_all_temp_backups() to shutdown

Hooked to: wp_delete_temp_updater_backups cron event

Since: 6.3.0

---

_wp_delete_all_temp_backups()

Actually deletes contents of wp-content/upgrade-temp-backup/.

_wp_delete_all_temp_backups()

Behavior:

• Requires filesystem credentials
• Iterates upgrade-temp-backup/ directory
• Recursively deletes all subdirectories

Since: 6.3.0
Access: Private

---

Transient Data Structures

update_core

object(
    'updates'         => array( /* offer objects */ ),
    'last_checked'    => int,  // Unix timestamp
    'version_checked' => string,
    'translations'    => array( /* translation objects */ ),
)

update_plugins

object(
    'last_checked'  => int,
    'checked'       => array( 'plugin/file.php' => 'version' ),
    'response'      => array( 'plugin/file.php' => object ),
    'no_update'     => array( 'plugin/file.php' => object ),
    'translations'  => array( /* translation objects */ ),
)

update_themes

object(
    'last_checked'  => int,
    'checked'       => array( 'theme-slug' => 'version' ),
    'response'      => array( 'theme-slug' => array ),
    'no_update'     => array( 'theme-slug' => array ),
    'translations'  => array( /* translation objects */ ),
)