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wp_start_object_cache()

This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.

Start the WordPress object cache.

Description

If an object-cache.php file exists in the wp-content directory, it uses that drop-in as an external object cache.

Source

File: wp-includes/load.php

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

	// Only perform the following checks once.
	if ( $first_init ) {
		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' );
	}

	/*
	 * 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( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'site-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'blog_meta' ) );
		wp_cache_add_non_persistent_groups( array( 'counts', 'plugins' ) );
	}

	$first_init = false;
}

Changelog

Version Description
3.0.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/wp_start_object_cache