wp_start_object_cache()

Source

function wp_start_object_cache() {
	global $wp_filter;
	static $first_init = true;

	// Only perform the following checks once.

	/**
	 * Filters whether to enable loading of the object-cache.php drop-in.
	 *
	 * This filter runs before it can be used by plugins. It is designed for non-web
	 * runtimes. If false is returned, object-cache.php will never be loaded.
	 *
	 * @since 5.8.0
	 *
	 * @param bool $enable_object_cache Whether to enable loading object-cache.php (if present).
	 *                                  Default true.
	 */
	if ( $first_init && apply_filters( 'enable_loading_object_cache_dropin', true ) ) {
		if ( ! function_exists( 'wp_cache_init' ) ) {
			/*
			 * This is the normal situation. First-run of this function. No
			 * caching backend has been loaded.
			 *
			 * We try to load a custom caching backend, and then, if it
			 * results in a wp_cache_init() function existing, we note
			 * that an external object cache is being used.
			 */
			if ( file_exists( WP_CONTENT_DIR . '/object-cache.php' ) ) {
				require_once WP_CONTENT_DIR . '/object-cache.php';

				if ( function_exists( 'wp_cache_init' ) ) {
					wp_using_ext_object_cache( true );
				}

				// Re-initialize any hooks added manually by object-cache.php.
				if ( $wp_filter ) {
					$wp_filter = WP_Hook::build_preinitialized_hooks( $wp_filter );
				}
			}
		} elseif ( ! wp_using_ext_object_cache() && file_exists( WP_CONTENT_DIR . '/object-cache.php' ) ) {
			/*
			 * Sometimes advanced-cache.php can load object-cache.php before
			 * this function is run. This breaks the function_exists() check
			 * above and can result in wp_using_ext_object_cache() returning
			 * false when actually an external cache is in use.
			 */
			wp_using_ext_object_cache( true );
		}
	}

	if ( ! wp_using_ext_object_cache() ) {
		require_once ABSPATH . WPINC . '/cache.php';
	}

	require_once ABSPATH . WPINC . '/cache-compat.php';

	/*
	 * If cache supports reset, reset instead of init if already
	 * initialized. Reset signals to the cache that global IDs
	 * have changed and it may need to update keys and cleanup caches.
	 */
	if ( ! $first_init && function_exists( 'wp_cache_switch_to_blog' ) ) {
		wp_cache_switch_to_blog( get_current_blog_id() );
	} elseif ( function_exists( 'wp_cache_init' ) ) {
		wp_cache_init();
	}

	if ( function_exists( 'wp_cache_add_global_groups' ) ) {
		wp_cache_add_global_groups(
			array(
				'blog-details',
				'blog-id-cache',
				'blog-lookup',
				'blog_meta',
				'global-posts',
				'networks',
				'network-queries',
				'sites',
				'site-details',
				'site-options',
				'site-queries',
				'site-transient',
				'theme_files',
				'translation_files',
				'rss',
				'users',
				'user-queries',
				'user_meta',
				'useremail',
				'userlogins',
				'userslugs',
			)
		);

		wp_cache_add_non_persistent_groups( array( 'counts', 'plugins', 'theme_json' ) );
	}

	$first_init = false;
}

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