Source

File: wp-includes/update.php

function wp_version_check( $extra_stats = array(), $force_check = false ) {
	global $wpdb, $wp_local_package;

	if ( wp_installing() ) {
		return;
	}

	// Include an unmodified $wp_version.
	require ABSPATH . WPINC . '/version.php';
	$php_version = phpversion();

	$current      = get_site_transient( 'update_core' );
	$translations = wp_get_installed_translations( 'core' );

	// Invalidate the transient when $wp_version changes.
	if ( is_object( $current ) && $wp_version !== $current->version_checked ) {
		$current = false;
	}

	if ( ! is_object( $current ) ) {
		$current                  = new stdClass;
		$current->updates         = array();
		$current->version_checked = $wp_version;
	}

	if ( ! empty( $extra_stats ) ) {
		$force_check = true;
	}

	// Wait 1 minute between multiple version check requests.
	$timeout          = MINUTE_IN_SECONDS;
	$time_not_changed = isset( $current->last_checked ) && $timeout > ( time() - $current->last_checked );

	if ( ! $force_check && $time_not_changed ) {
		return;
	}

	/**
	 * Filters the locale requested for WordPress core translations.
	 *
	 * @since 2.8.0
	 *
	 * @param string $locale Current locale.
	 */
	$locale = apply_filters( 'core_version_check_locale', get_locale() );

	// Update last_checked for current to prevent multiple blocking requests if request hangs.
	$current->last_checked = time();
	set_site_transient( 'update_core', $current );

	if ( method_exists( $wpdb, 'db_version' ) ) {
		$mysql_version = preg_replace( '/[^0-9.].*/', '', $wpdb->db_version() );
	} else {
		$mysql_version = 'N/A';
	}

	if ( is_multisite() ) {
		$user_count        = get_user_count();
		$num_blogs         = get_blog_count();
		$wp_install        = network_site_url();
		$multisite_enabled = 1;
	} else {
		$user_count        = count_users();
		$user_count        = $user_count['total_users'];
		$multisite_enabled = 0;
		$num_blogs         = 1;
		$wp_install        = home_url( '/' );
	}

	$query = array(
		'version'            => $wp_version,
		'php'                => $php_version,
		'locale'             => $locale,
		'mysql'              => $mysql_version,
		'local_package'      => isset( $wp_local_package ) ? $wp_local_package : '',
		'blogs'              => $num_blogs,
		'users'              => $user_count,
		'multisite_enabled'  => $multisite_enabled,
		'initial_db_version' => get_site_option( 'initial_db_version' ),
	);

	/**
	 * Filter the query arguments sent as part of the core version check.
	 *
	 * WARNING: Changing this data may result in your site not receiving security updates.
	 * Please exercise extreme caution.
	 *
	 * @since 4.9.0
	 *
	 * @param array $query {
	 *     Version check query arguments.
	 *
	 *     @type string $version            WordPress version number.
	 *     @type string $php                PHP version number.
	 *     @type string $locale             The locale to retrieve updates for.
	 *     @type string $mysql              MySQL version number.
	 *     @type string $local_package      The value of the $wp_local_package global, when set.
	 *     @type int    $blogs              Number of sites on this WordPress installation.
	 *     @type int    $users              Number of users on this WordPress installation.
	 *     @type int    $multisite_enabled  Whether this WordPress installation uses Multisite.
	 *     @type int    $initial_db_version Database version of WordPress at time of installation.
	 * }
	 */
	$query = apply_filters( 'core_version_check_query_args', $query );

	$post_body = array(
		'translations' => wp_json_encode( $translations ),
	);

	if ( is_array( $extra_stats ) ) {
		$post_body = array_merge( $post_body, $extra_stats );
	}

	$url      = 'http://api.wordpress.org/core/version-check/1.7/?' . http_build_query( $query, null, '&' );
	$http_url = $url;
	$ssl      = wp_http_supports( array( 'ssl' ) );

	if ( $ssl ) {
		$url = set_url_scheme( $url, 'https' );
	}

	$doing_cron = wp_doing_cron();

	$options = array(
		'timeout'    => $doing_cron ? 30 : 3,
		'user-agent' => 'WordPress/' . $wp_version . '; ' . home_url( '/' ),
		'headers'    => array(
			'wp_install' => $wp_install,
			'wp_blog'    => home_url( '/' ),
		),
		'body'       => $post_body,
	);

	$response = wp_remote_post( $url, $options );

	if ( $ssl && is_wp_error( $response ) ) {
		trigger_error(
			sprintf(
				/* translators: %s: Support forums URL. */
				__( 'An unexpected error occurred. Something may be wrong with WordPress.org or this server&#8217;s configuration. If you continue to have problems, please try the <a href="%s">support forums</a>.' ),
				__( 'https://wordpress.org/support/forums/' )
			) . ' ' . __( '(WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.)' ),
			headers_sent() || WP_DEBUG ? E_USER_WARNING : E_USER_NOTICE
		);
		$response = wp_remote_post( $http_url, $options );
	}

	if ( is_wp_error( $response ) || 200 !== wp_remote_retrieve_response_code( $response ) ) {
		return;
	}

	$body = trim( wp_remote_retrieve_body( $response ) );
	$body = json_decode( $body, true );

	if ( ! is_array( $body ) || ! isset( $body['offers'] ) ) {
		return;
	}

	$offers = $body['offers'];

	foreach ( $offers as &$offer ) {
		foreach ( $offer as $offer_key => $value ) {
			if ( 'packages' === $offer_key ) {
				$offer['packages'] = (object) array_intersect_key(
					array_map( 'esc_url', $offer['packages'] ),
					array_fill_keys( array( 'full', 'no_content', 'new_bundled', 'partial', 'rollback' ), '' )
				);
			} elseif ( 'download' === $offer_key ) {
				$offer['download'] = esc_url( $value );
			} else {
				$offer[ $offer_key ] = esc_html( $value );
			}
		}
		$offer = (object) array_intersect_key(
			$offer,
			array_fill_keys(
				array(
					'response',
					'download',
					'locale',
					'packages',
					'current',
					'version',
					'php_version',
					'mysql_version',
					'new_bundled',
					'partial_version',
					'notify_email',
					'support_email',
					'new_files',
				),
				''
			)
		);
	}

	$updates                  = new stdClass();
	$updates->updates         = $offers;
	$updates->last_checked    = time();
	$updates->version_checked = $wp_version;

	if ( isset( $body['translations'] ) ) {
		$updates->translations = $body['translations'];
	}

	set_site_transient( 'update_core', $updates );

	if ( ! empty( $body['ttl'] ) ) {
		$ttl = (int) $body['ttl'];

		if ( $ttl && ( time() + $ttl < wp_next_scheduled( 'wp_version_check' ) ) ) {
			// Queue an event to re-run the update check in $ttl seconds.
			wp_schedule_single_event( time() + $ttl, 'wp_version_check' );
		}
	}

	// Trigger background updates if running non-interactively, and we weren't called from the update handler.
	if ( $doing_cron && ! doing_action( 'wp_maybe_auto_update' ) ) {
		/**
		 * Fires during wp_cron, starting the auto-update process.
		 *
		 * @since 3.9.0
		 */
		do_action( 'wp_maybe_auto_update' );
	}
}